At least a thousand townspeople crowded into the catheral at nearby La Laguna tonight in an interfaith service to mourn the hundreds who died Sunday when two jumbo jets collided at the airport here.

The service interrupted a busy day of negotiations as U.S. officials sought Spanish authorities' permission to take 326 bodies from the Pan American World Airways 747 to a special facility at McGuire Air Force Base in New Jersey for faster identification.

Most of the bodies are badly charred. A U.S. team of pathologists and forensic dentists has been here since Tuesday but has not been permitted to assist the Spanish officials operating a makeshift morgue in a hanger.

Controversies over the cause of the accident and the medical care of the survivors continued today in the delicate aftermath of the collision between Dutch and American planes on Spanish soil.

The crash, which left 577 persons dead, was aviation's worst disaster. The latest two victims were a woman who died while being flown to the United States and a man who died in the hospital here.

The controversies were forgotten for more than an hour tonight as a Catholic mass was followed by short messages from a Dutch Reformed minister from the Netherlands, an Anglican priest from Tenerife and a leader of the local Jewish community, who wore a yarmulke as he spoke under the figure of Christ on the cross.

Four stewardess who survived the crash attended the service, as did many high-ranking military officers, the Spanish air minister, and American officials of Pam Am, the National Transportation Safety Board and other U.S. organizations.

There were a few relatives of victims, including Mary Kay Walters of San Francisco, who lost both parents. Her mother was killed in the crash; her father, Col. Alexander Waters, died Tuesday in the hospital here after his daughter had seen him.

Miss Walters took communion during the Catholic service. The service, she said afterward, "helped."

"It shows that people in the world care. It was touching to hear people crying in the back of the church." Her parents, like most of those on the Pan Am plane, were from the Los Angeles area.

Identification of the bodies may take weeeks, but death certificates cannot be issued, nor insurance and other benefits paid until the process is completed.

Because of the way the KLM 747 rammed through the Pan Am jet, the bodies were segregated on the ground and it was easy to tell which airplane they came from, investigators said. Most of the bodies are intact, according to doctors, but so badly burned that identification will probably be done primarily through dental charts.

If Spanish authorities release the bodies, they will be flown to a special facility, established to identify Vietnam war victims, at McGuire Air Force Base.

Pan Am and safety board officials defended the decision Tuesday to fly 54 survivors from Tenerife to Brooke Army Medical Center in San Antonio, Texas.

The director of the Tenerife Hospital, Dr. Eufedio Gambin, had complained about the transfer, which was permitted only after the senior American doctor - an Air Force physician with the U.S. embassy in Madrid - agreed to accept all responsibility. Sixteen survivors remain in the hopital here.

A clearer picture of how the accidents may have occured began to emerge as Spanish Dutch and American investigators sifted evidence, but the central question - why - remains unanswered.

The Dutch Civil Aviation announced Monday that the KLM 747 captain began to take off without the proper air tarffic control clearance and struck the Pan Am 747, which was still on the runway. Neither Dutch or U.S. officials regard that as the final answer, however.

"It is inconceivable," KLM said, that their pilot would have done such a thing. The pilot, Z.A. Velduizen van Zanten, 51, was chief instructor of pilots for KLM. He died along with the other 247 people aboard. Several experts said privately yesterday that they doubt that an unauthorized takeoff could be the total explanation.

Douglas Dreyfus, a safety board invetigator and chief U.S. negotiator here because of international aviation procedures, said in an interview that the recordings of conversations in both cockpits would be "critical" in determination of the cause. Neither recording has been played, but both have been recovered from the wreckage.

"When we got that we can confirm the tower transmission and correlate it with any discussion in the cockpit. This does not mean the air traffic control tape [as provided by Spanish officials] is correct. But how do we know that the transmission was received as sent - that an important word was not lost?"

Dutch reporters today were pursuing the notion that Spanish officials might have tampered with the air traffic control tape to absolve themselves of responsibility. U.S. officials know of no evidence of tampering, sources [WORD ILLEGIBLE]

Dutch and U.S. officials are seeking Spanish permission to have the cock-pit recordings from both 747s flown the Washington for analysis. The recordings would remain in Spanish custody, and Spanish approval is expected.

According to investigators and others familiar with the evidence, this is what happened Sunday.

A terrorist bombing in the airport at Las Palmas, on nearby Grand Canary Island, forced many large jets including the Pan Am and KLM flights, to be diverted to Tenerife.

When the KLM captain decided to take on more fuel, delaying the two planes' takeoffs, the Pan Am crew considered taking off first, but there was not enough room to taxi past the Dutch plane.

After the refueling was completed, first the KLM jet, then the Pan Am plane started down the runway from northwest to southeast. The KLM plane reached the far end, turned around into the wind and started to take off.

The Pan Am plane was still on the runway.

There have been charges that the Pan Am pilot, Victor Grubbs, did not obey a direction to turn off the runway at an earlier point, but Pan Am's vice president for operations, William Waltrip dismissed that as "a bunch of crap."

Waltrip said he had heard the recording of air traffic control communication, and the last transmission from the Pan Am crew was to the effect that the plane was still on the runway and would tell the tower when it had cleared it. The tower's instructions to both planes were on the same frequency.

The runway was foggy at the time of the crash, and it is not known whether it could be seen clearly from the control tower.

The KLM jet was already rolling down the runway at nearly 165 miles an hour, and when the Pan Am crew saw its lights coming toward them they swerved the Pan Am plane sharply to the left.

In the last seconds, investigations believe the Dutch captain made a desperate attempt to get his jet over the Pan Am 747, which was turned at a 45-degree angle by that time.

Most officials think that the KLM's nose wheel was off the ground when its undercarriage and belly plowed through the Pan Am jet just behind the cockpit. The KLM's wing sliced off the top of the hump housing the first-class lounge.

Today, cleanup crews were busy bull-dozing bits of the two jumbo jets off the runway, and small planes were able to take off and land on the half of the runway that has returned to service. Seven big jets, including two jumbos, are still stranded here.

[In Fort Dix, N.J., the Associated Press quoted Pan Am pilot Grubbs as saying: "Looking back at the rubble, I first thought to myself, 'Look what I've done to those people.' But in my heart I knew that it wasn't my fault."]

[Asked if Spanish news accounts were correct in quoting him as saying "We are still on the runway . . . What's he doing? He'll kill us all!," Grubbs replied: "Yes, I said that. I'll never forget that instant."]