A Japan Air Lines jumbo jet carrying 524 persons crashed into a forested mountainside near Tokyo and burned last night.

By this morning, rescue teams searching the site had found seven survivors, three of them unconscious, according to Japanese television reports.

The teams were reported to have encountered an undisclosed number of dead bodies at the remote site, where wreckage from the plane, a Boeing 747, is strewn over an area of more than a mile.

The plane crashed shortly after 7 p.m. last night after taking off from Tokyo's Haneda Airport on a domestic flight to Osaka, Japan's second-largest city.

Two Americans were reported to be on the plane.

The impact occurred about 40 minutes after the crew reported by radio that the plane's rear right door was "broken" and that they wanted to make an emergency landing.

Despite the discovery of survivors, there was little hope that many people lived through the crash, which reduced the jet to twisted scrap metal. The crash seemed likely to rank as the world's largest single-plane disaster in the history of commercial aviation.

Television identified two of the survivors as Hiroko Yoshizaki, 35, and Mikiko Yoshizaki, 8, apparently the woman's daughter. A third survivor was said to be 12-year-old Keiko Kawakami, and the fourth was a boy.

Live images from television cameras on the ground at the crash site, located about 60 miles northwest of Tokyo, showed scenes of devastation, with bodies, baggage and scrap metal scattered through a jagged clearing torn out by the impact of the plane. One survivor was shown being carried away on a stretcher.

Japanese military helicopters are ferrying rescuers and supplies into the site, which cannot be reached by road. Altogether, about 5,000 persons have been mobilized for the effort.

Aviation experts last night speculated that hijacking or terrorism could have played a role but said that so far there is no direct evidence pointing in that direction. Thunderstorms also were reported to have been in the area.

Given the rugged terrain, aviation experts held out little hope that there would be many survivors.

The crash held the potential to almost equal the death toll of commercial aviation's worst disaster, the collision of Pan American World Airways and KLM jumbo jets on a runway in Tenerife on the Canary Islands in 1977 with the loss of 582 lives.

The current worst single-plane crash involved a Turkish Air Lines DC10, which crashed near Paris, killing 346 persons in 1974.

The plane was heavily loaded, carrying 509 passengers and a crew of 15. It reflected the heavy travel that occurs annually in Japan during the Obon religious holiday, a time when Japanese families traditionally visit family homes to honor their ancestors.

Some of the passengers were said to be families returning from a technology expo at Tsukuba outside Tokyo.

[In New York, a spokesman for the airline identified the two American passengers as Edward A. Anderson Sr., 48, of Englewood, Colo., and Michael Hanson, 40, of Aurora, Colo., according to United Press International.]

Twenty-one of the passengers were reported to be foreigners.

Reported to be among the passengers was Kyu Sakamoto, a Japanese pop singer whose song "Sukiyaki" won him international fame in 1963.

The passengers also reportedly included Hajimu Nakano, the president of the Hanshin Tigers professional baseball team, and Umio Uraumi, president of House Food Industrial Co., one of the firms that was targeted in a widely publicized recent extortion plot by a group calling itself the "man with 21 faces."

Relatives of the passengers gathered in hotels in Tokyo and Osaka during the night as national television broadcast passenger lists. Close to 1,500 relatives of people aboard the jet have been taken to the city of Fujioka near the crash site to await the results of the search. Bodies will be moved there for identification.

Many relatives were flown to Tokyo from Osaka aboard a special Japan Air Lines flight this morning. Airline president Yasumoto Takagi stood at the bottom of the passenger stairs and bowed deeply to them repeatedly as they got off the plane

Relatives wee being bused toward the crash site this morning.

The jet was also reorted to be carrying radioactive medical isotopes. A spokesman for the airline told Reuter that the material would not be a health hazard unless it was held close to a person's body for a long period of time.

Details of the flight were sketchy, but official announcements and media reports gave the following account.

The four-engine plane, a Boeing 747SR operating as Japan Air Lines Flight 123, left the gate at Tokyo's Haneda Airport at 6:04 p.m. to make the 50-minute flight to Osaka. Haneda is Tokyo's airport for domestic flights. The initials SR indicate that the plane is a modified 747 designed to carry large numbers of passengers on short-range flights.

The plane took off at 6:12 p.m., about four minutes behind schedule. It was scheduled to proceed south over Tokyo Bay before making a right turn to take it down the coastline of Honshu Island toward Osaka.

The pilot was identified as Masami Takahama, a veteran pilot with more than 12,400 hours of flight time.

At 6:25, the crew transmitted a nonverbal distress signal and then verbally reported that it was about 23 miles west of Oshima Island, which lies about 75 miles south-southwest of Tokyo.

The crew requested permission to descend from about 23,800 feet to 21,800 feet, said it wanted to return to Haneda and requested radar guidance.

Air traffic controllers told the crew to fly east. However, radar tracking showed that the jet maintained its westerly course. At 6:27, the crew radioed "emergency" and, in English, the words "unable to control."

Four minutes later, the crew radioed that it wanted to go back to Haneda.

Ten minutes after that it radioed the Japan Air Lines operations center that the right rear door was "broken." Pressure in the passenger cabin was falling, the crew said, and the plane was making an emergency descent.

At 6:46, ground controllers asked the crew whether Haneda should be told to prepare for an emergency landing. The response, reportedly in a panicky voice, was: "Yes, please do!" At about that time, the crew again said it was "unable to control."

Radar showed that by this time the plane had turned and was proceeding along an S-shaped route to the north, passing over land.

At 6:54, crew members again said that they were "unable to control." They did not know where they were and asked controllers to tell them. The ground responded that the plane was 50 miles northwest of Haneda and 28 miles west of Kumagaya. The crew responded "roger."

Ground controllers then told the crew that both Haneda and Yokota Air Base, an American and Japanese military facility outside Tokyo, were ready for an emergency landing. There was no reply.

The plane vanished from radar screens at 6:57 p.m. at a point about 66 miles northwest of Haneda and at an altitude of about 9,600 feet.

The plane struck the 6,929-foot tall Ogura Mountain near the borders of Gumma and Nagano prefectures at an elevation of about 5,100 feet. Elevation of the crash site seems to be about 5,100 feet.

The Japanese Cabinet convened an emergency meeting last night at 11 to plan the rescue operation. News reports said that about 4,000 persons, including more than 3,000 personnel from the Self-Defense Forces, as the military here is called, would take part. Two American crash specialists were sent to assist in the investigation.