Rescue workers continued picking through the rubble of the American Embassy here today as U.S. officials said that 46 persons, 16 of them Americans, were confirmed dead or were still missing and presumed dead beneath the heavy debris.

Among the seven Americans who were confirmed dead were three Washington area residents, including Robert Clayton Ames whom a CIA spokesman described as the agency's top Middle East analyst. Nine other Americans were listed as missing. Details on Page A22.

It was impossible to get an accurate total count of casualties, since the number of deaths reported by U.S. officials here dealt only with those persons known to have been inside the building at the time of the blast.

The explosion also apparently struck passing motorists and strollers. The morgue at the nearby American University of Beirut had 35 charred and mangled bodies, six of which were pulled from the rubble today.

Meanwhile, U.S. Ambassador Robert Dillon sought to reaffirm that the U.S. commitment to Lebanon will continue to be strong. In a brief session with reporters as he stood on the rear bumper of a Red Cross van in front of the embassy this morning, Dillon said, "The work of this embassy will continue."

"Paramount among essential business is our work for the withdrawal of all foreign forces from Lebanon and our support for the Lebanese authorities as they work for full restoration of Lebanese sovereignty," he said. It is only by restoring Lebanese control over all areas of the country, Dillon added, "that terrible tragedies like the one we experienced yesterday can be avoided in the future."

Dillon said it was unclear how the bomb, which exploded at 1:05 p.m., was detonated, but he said that "two competent eyewitnesses" reported seeing a large van laden with explosives force its way into the embassy driveway before the blast.

Reports yesterday speculated that the bomb might have been remote controlled. Others suggested it was the work of a "suicide terrorist" who was killed in the explosion. Authorities today still had not established precisely what happened.

Although a group calling itself Islamic Jihad Organization, which means Moslem holy war, claimed responsibility in a telephone call to a news agency immediately after the blast, other newspapers today said they received similar calls from different groups during the night.

Dillon said there had been no threats before the explosion. Asked if he the embassy, with its open driveway guarded by Lebanese police, had been thought secure, the ambassador said he had not been satisfied. He said there had been continuous work to improve security.

U.S. Marines cordoned off the area around the embassy as Red Cross workers continued a search for the dead and huge cranes and earth-moving equipment took apart the shattered seven-story pink structure slab by slab.

The acrid stench of tear gas filled the air as workers struck containers of the gas that had been stored in the embassy, presumably to be used for riot control.

Embassy staff members said operations had moved to Dillon's residence and to an apartment building a few blocks from the embassy on the Beirut seafront. Embassy sources said all sensitive, classified material and codes had been removed from the building after the explosion.

The sources did not know where new quarters would be established. They estimated that it would take two to three years to build a new structure.

For Diyala Ezzedine, a student at the American University of Beirut and a Red Cross volunteer who worked through the night in the rescue operations, the destruction of the embassy hit with special force in a country where bombs and violence have become routine in eight years of war.

"The American Embassy was always a symbol of security," she said today as she stood in front of the ruins.

The array of warring political factions uniformly condemned the attack, but they pointed accusing fingers at their favorite enemies.

The Christian rightist newspaper Al Amal strongly suggested that Palestinians were responsible and said in a front-page editorial that Palestinian camps in Lebanon "must be cleared of terrorist hide-outs, without falling in the trap of 'human rights' as was the case in the past."

The leftist As Safir newspaper suggested that Israel was behind the explosion, recalling in a front-page editorial what it said were reports in 1954 that Israel had ordered the planting of explosives in the library of the U.S. Embassy in Cairo to head off better U.S.-Egyptian relations.

The privately owned Central News Agency reported that an "official source" told them the bomb was directed against U.S. special Middle East envoys Philip C. Habib and Morris Draper, who were scheduled to have been in the embassy when the explosion occurred. Habib and Draper were meeting with Lebanese Foreign Minister Elie Salem at the Lebanese presidential palace at the time.

U.S. officials had no immediate comment on the report, which said Habib and Draper had been delayed in returning to the embassy.

The Central News Agency said its source said this information indicated that the attack was not the work of amateurs but sophisticated terrorists with access to the sensitive information of Habib and Draper's schedules.

Habib visited the site today before flying on to Israel to continue his mediation efforts in the Lebanese peace talks. Dillon went to the American University hospital today, where 19 persons were admitted with burns, fractures and deep cuts. It was reported here that about 100 others sustained minor injuries.

There were many horrific memories of the explosion. Dillon recalled being thrown suddenly to a floor and covered with rubble. An aide used the staff of an American flag to clear the debris off him.

Embassy political officer Ryan Crocker remembered that he had pencil in hand and was editing a long cable when the bomb went off.

"Suddenly that flash. Whoosh. No cable, no pencil and I was thrown off to the side," he said.

Paul Siekert, the embassy's assistant general services officer, who arrived here Friday, said, "I can't really remember anything. There was an explosion. I was knocked unconscious. I woke up in an ambulance."