Spanish officials said today that a misunderstanding involving the pilots of a Pan American Airways 747 and a Dutch KLM 747 and the control tower may have caused the crash that took nearly 600 lives in history's worst air disaster.

The number of known dead fluctuated during the day both KLM and Pan Am issued revised casualty lists late today that put the number of dead at 576, with 68 survivors.

KLM said all 248 people aboard its jet, including four Americans from Rochester, N.Y., died. The Dutch plane, roaring down the runway at about 150 miles per hour on takeoff, ripped through the American jet yesterday afternoon. Pan American said 328 died aboard its plane and 68 survived. Estimates of future insurance claims ranged from $200 million to $250 million.

Preliminary findings at Los Rodeos Airport left in doubt who was at fault in the crash, but officials said it was clear that the Pan American plane, laden with tourists from the Los Angeles area, turned into the path of the KLM plane.

Officials said it was not known if the KLM jet had been cleared for takeoff, but both planes were on the runway, with the KLM 747 at its head and the Pan Am on a section used for taxing.

"Under certain circumstances this is allowed," an officials said. The investigation, he said, "will answer whether these circumstances existed at the time."

In Amsterdam, the president of KLM, Sergio Orlandini, claimed that part of the taxiway, which he said is parallel to the main runway, is too narrow for jumbo jets, so the widebodied planes use a section of the runway to move up to the assembly point to prepare for takeoff.

An official in the control tower said yesterday that the planes collided in "poor visibility," and reporters were told today that the field has no ground radar.

Subject to frequent fogs and unpredictable winds, the airport is considered one of the most dangerous in Spanish territory. During the past 21 years it has been the scene of six other accidents, which claimed 252 lives.

The question of air safety throughout all the Spain has been the subject of sharp debate for several months. Last year air controllers at fields around the country staged a month long, go-slow, work-to-rules strike to protest what they said was outdate radar and other equipment, manned by too few people working too long hours. Their slowdown followed two reported near misses between planes.

The civil governor of Tenerife, Antonio Oyarzabal, said the buildup of air traffic at Los Rodeos because planes were diverted from Las Palmas after a bomb blast there had nothing to do with the accident. "Of six planes diverted, four left here completely normally," he told a press conference.

Some foreign pilots criticed the quality of English - the international language for flight operations - spoken by Tenerife controllers. Victor Jauering, vice president of the West German airline pilots' association, said the Spanish controllers speak heavily accented English.

Gove, Oyarzabal told his news conference that in the last minutes before the accident the tower told the KLM to go to the head of the runway and ordered the Pan Am 747 to taxi to a standby position.

"Both planes took to the runway," he said. "The key point is whether the KLM plane had been given orders to take off."

Survivors said the KLM jet struck the PAN AM jet broadside, just after of the first-class section. Momemtum carried the huge plane - fully loaded 747s weigh more than 200 tons - right through the American jet and several hundred more yards down the runway.

The Spanish news agency Cifra said the flight recorder tapes of a conversation between the Pan American pilot and the control tower showed that the pilot apparently misunderstood instructions to stay on a taxiway, and turned onto the takeoff runway by mistake.

Among the survivors was Capt. Victor S. Grubbs, on Centerport, N.Y., pilot of the Pan Am plane. Cifra quoted him as blaming ground fog for the collision: "We did not see anything until it happened."

A 41-member team of the U.S. National Transportation Safety Board arrived to help Spanish authorities in the investigation. A three-man American team of pathologists headed by William Reals, vice president for medical affairs at St. Joseph Medical Center in Wichita, Kans., left yesterday to join the investigation, and eight officals came from the U.S. embassy in Madrid to aid survivors and handle the personal affairs of the dead. [TEXT OMITTED FROM SOURCES] present at Oyarzabal's press conference were Air Minister Gen. Carlos Franco, and International Air Transport Association President Manuel del Pradoy Colon, who is also the president of tee Spanish airline Iberia.

KLM said four Americans living in the Netherlands were killed aboard the Dutch jet: D.R.E. Gilles, 49, and his wife, Jane, 48, of Rochester, N.Y.; Ms. T. Twist, 21 or 21, also of Rochester, and her 21-month-old dauther, Melissa. Gilles and the young woman worked for the Rank Xerox Co. in Venray, The Netherlands.

The worst previous air disaster was the crash of a Rurkish Airways DC10 near Paris March 3, 1974, killing 346 people.

Insurance specialists in London and New York estimated that claims arising from yesterday's accident would total between 200 million and 250 million.

A spokesman for Lloyd's of London said the two 747s were probably insured for about $25 million each.

Passenger liability for the hundreds killed and injured could bring claims to between $100 million and $200 million, the spokesman said.