U.S. military personnel, finding "smaller bodies under larger bodies and children under those," discovered today that as many as 780 Americans died in Jonestown last Saturday when cult leader Jim Jones led them to commit suicide.

A week-old estimate of just over 400 bodies, apparently based only on a rough count made by the Guyanese authorities, who were the first to reach the death scene last weekend and did not move the bodies, was "found to be seriously in error" today, according to a U.S. spokesman. When U.S. military personnel packing the dead in plastic bags neared 400, they realized there were many more to go.

"The way all this happened was that nobody [in the U.S. military task force] stopped to count" when they reached Jonestown early this week, said another U.S. official. "But as they bagged the bodies, they noticed the pile wasn't going down."

"We simply began to discovcer more and more and more bodies," said Air Force Capt. John J. Moscatelli, spokesman for the U.S. military task force here.

"Under adults we found smaller adults and children, and more small babies than anticipated."

Most of the previously overlooked bodies were found at the bottom of what turned out to be a three-and four-deep pile off to the side of the open-air pavilion. There Jones supervised the distribution of the poisoned Kool-Aid to followers herded around him, encircled by armed guards. Jones himself was later found shot to death at the front of the pavilion.

Today's unexpected discovery was a swift, shocking blow to both U.S. authorities and relatives of Peoples Temple church members that both doubled the death toll at Jonestown and snuffed out hope that many more survivors might be found.

Just yesterday, U.S. officials here raised doubts whether there really were 300 to 400 more Jonestown residents who had fled into the surrounding forest.

"You don't know whether to be relived or horrified," said U.S. Consul Douglas Ellis who has been the liaison between the embassy here and the 32 known survivors of Jonestown as well as relatives of Jonestown residents seeking to discover whether their loved ones are dead or alive.

"It appears that there may not be anybody to search for and rescue."

All week long, officials had agonized over the mystery of what had happened to several hundred Jonestown residents apparently not counted in the original estimate of about 400 dead. U.S. military helicopters were scheduled to begin flying over the dense rain forest surrounding Jonestown broadcasting loudspeaker appeals to any survivirs who might have fled there.

Now, however, the numbers that had been in contention here all week appeared to be adding up.

The Guyanese government said today that its records showed 950 Peoples Temple church members had entered Guyana since the Jonestown agricultural commune was founded five years ago.

Meanwhile, the U.S. Embassy todaexamined and photocopied 803 U.S. passports the Guyanese authorities had recovered in Jonestown. The copies will be sent to Washington for a determination of how many persons they cover. That number could be more than 800 because some children may have traveled on parents' passports, and others have been born in Jonestown. Markers in a small cemetery found in Jonestown indicate that only about 10 residents died there before last weekend.

Against that evidence are these numbers:

As many as 780 bodies were counted in Jonestown by this afternoon.

Four other Peoples Temple church members were killed inside the Georgetown headquaters Saturday night, and one defector from the commune was shot to death along with Rep. Leo J. Ryan (D-Calif) and three newsmen after they left Jonestown earlier Saturday.

32 other Jonestown residents who escaped Saturday's violence.Some of them left with Ryan's group and survived the ambush at the Port Kaituna leading strip near Jonestown, and others slipped out of onestown before and during the forced mass suicide.

46 other Peoples Temple members still under armed guard and horse arrest inside the Georgetown headquaters house. They include Jim Jones' son and top lieutenant, Steve Jones, and other members of the Jonestown basketball team, which was in Georgetown playing the Guyanese national team last weekend.

According to Guyanese police sources, some cult members now in that house are being investigated for the murder of Peoples Temple member and house resident Sharon Amos Harris and her three children, who were found in the Georgetown house Saturday night with their throats slashed. Survivors from Jonestown have told authorities that members of the basketball team were trained sharp-shooting security guards who practiced with firearms in the forest around Jonestown.

Four other Jonestown resi'ents found aboard the cult's coastal freighter, the Albatross, when it landed in Trinidad this week after leaving Guyana well before last weekend's violence. Those four are being temporarily held by Trinidad authorities, who are in communication with Guyana.

Two or three more Jonestown residents reportedly found by a Guyana Defense Force patrol boat aboard the cult's fishing boat, the Cudjoe, three days ago just 20 miles north of its Port Kaituma dock. They are being questioned by police here. A third boat named the Marcellene after Jim Jones' wife, is still missing.

These numbers make a total of between 850 and 900 Peoples Temple members now accounted for in Guyana.

The only remaining lead on more possible survivors from Jonestown is a report from Venezuela that the pilot of a Venezuelan military plane patrolling its disputed border with Guyana saw what appeared to be 30 or 40 people heading west toward the border from the rain forest around Jonestown and Port Kaituma. Guyanese government spokesmen denied knowledge of such a report.

Meanwhile the grim airlift of bodies from Jonestown continued at a brisk pace. By midday 485 bodies had been taken in plastic body bags by helicopter from Jonestown to Timehri International Airport, where they were transfered to aluminum coffins and put onto military cargo planes bound for the U.S. Air Force base in Dover, Del.

This afternoon, the government of Prime Minister Forbes Burnham made it's first public report to the guyanese people about the Jonestown affair. Deputy Prime Minister Ptolemy Reid delivered the report in a 15-minute statement to Parliament that was broadcast across the country by the Guyanese Broadcasting Service.

Reid's address, in the crowded chamber of the 150-year-old pink and white neoclassical parliament building was essentially a chronological listing of the steps the government took after the Jonestown violence occured. Nothing new was revealed.

Reid a large black man with a full grey beard, who like the 53 members of the National Assembly wore an open-necked shirt and no coat in the tropical heat, also stated his nation's "deep regret and sympathy" to the American people for the tragedy that occurred at Jonestown.

He pointedly indicated throughout his statement that he believed his government had acted as quickly as possible at every stage of the emergency.

For example, he said that after the ambush of Ryan's party at the Port Kaituma airstrip, "one of the more seriously injured persons was conveyed that very evening to the hospital in Georgetown where a medical team was on standby and the injured person received immediate attention. Others were flown out the following day."

Later, he pointed out that, after the first report was received of a possible mass murder or suicide at Jonestown, the Guyanese Defense Force mobilized troops as quickly as possible at Matthews Ridge, 20 miles away, and "moved by foot and train to Port Kaituma and then to Jonestown Sunday on foot.

"It should be noted that all this was done under very adverse conditions," Reid said, explaining that the terrain was very rough and falling heavily.

Reid ended his address by saying that he wished to "reiterate our deepest sympathy to all who are grieving. We mourn with all of them."

After finishing, Reid strode hurriedly off the floor, pushing his way through reporters and bystanders. He was followed by catcalls from members of the opposition Peoples Progressive Party, whose acting leader tried to insist that Reid answer questions.

When the speaker of the house ruled that, for technical reasons, the Jonestown matter could not be discussed on the floor, cries of "Shame. shame," and "cover up" rang out.

Some members of the opposition party and its newspaper here have raised questions about the apparently close relationship between Ptolemy Reid in particular and the Burnham government generally with Jim Jones.Jones and Reid met on several occasions and the Burnham government has been accused here of looking the other way when the Jonestown commune using its three boats, allegedly shipped out produce and brought in supplies without going through customs.

For the foreign reporters who filled the press seats in the National Assembly to hear Reid, the most important thing he did in his address was make the first reference those reporters heard today to the new, greatly enlarged body count at Jonestown. CAPTION: Picture 1, Rows of bodies photographed at Jonestown Monday were among those that concealed other bodies discovered by searchers yesterday. Copyright (c) 1978, Frank Johnston - The Washington Post; Picture 2, Children's bodies were discovered under the bodies of adults. Copyright (c) 1978, Frank Johnston - The Washington Post; Picture 3, Relief workers carry a large wooden chest found in the home of cult leader Jim Jones. Copyright (c) 1978, Frank Johnston - The Washington Post; Picture 4, U.S. military personnel carry plastic bags with bodies of suicide victims removed from Jonestown. UPI; Picture 5, Empty bottles of poison and other drugs found at Jonestown. Copyright (c) 1947, Frank Johnston - The Washington Post.