For the US intelligence community, the loss of the EP-3E is a serious event almost unparallelled for four decades - since Gary Power's U-2 was shot down over the Soviet Union. Paul Beaver of Jane's Defence

China has almost certainly already searched a US spy plane which made an emergency landing on its territory, despite warnings to stay away, according to the US ambassador in Beijing.

The aircraft is currently being held near Lingshui on the southern island of Hainan after colliding on Sunday with a Chinese fighter jet, and is packed with top-secret monitoring equipment.

A US official said US diplomats were meeting with the 24-member crew of the plane on Tuesday afternoon.

Earlier, Ambassador Admiral Joseph Prueher said: "We have every reason to think that the Chinese have been all over the airplane."

China has maintained it has the right to inspect the plane, with President Jiang Zemin insisting the United States must "bear full responsibility" for Sunday's collision.

Beijing has accused the Navy surveillance EP-3 of ramming its aircraft, but the US says it was probably an accident caused by the Chinese plane.

The crew have been stranded on Hainan since making an emergency landing there following the mid-air clash.

According to US officials, the last message from the crew said Chinese soldiers were boarding the EP-3 plane.

US President George W Bush has called on China to release the plane "without further tampering".

But Chinese Foreign Ministry spokesman Zhu Bangzao said on Tuesday: "Based on Chinese law, and international practice, we have the right to conduct an investigation."

Mocking the American claim that the plane is protected by international law from outside inspection without US permission, Mr Zhu smiled and said: "If this plane is sovereign American territory, how did it land in China?"

Analysts say it would be catastrophic for the US if the Chinese gained access to the aircraft's computers and hard disks.

US concern
Although the Chinese have said the spy plane's crew are safe and well, relatives in the US are increasingly worried.

Ken Cecka's brother, David, is among those detained.

"We want to hear [David's] voice on the telephone and know he is on his way home," he said.

Tom Crandall, whose son Tom is also a crew member, said: "I'm a nervous wreck. I'm quivering. My knees are shaking."

"What I'm worried about is what are they doing to him now? Are they interrogating him? Are they beating him?."

Staff at Whidbey Island Naval Air Station in Washington State where the crew is based tied yellow ribbons in honour of their colleagues.

The search for the missing Chinese pilot, who reportedly parachuted from his plane, is continuing.

The US has ordered three of its warships in the South China Sea region to move out of the area after Chinese officials ignored their offers of help in the search.

The US spy plane that made an emergency landing in China on Sunday after colliding with a Chinese fighter jet belongs to an elite highly classified reconnaissance unit.

The EP-3 Aries is the US Navy's principal long-range electronic surveillance aircraft, packed with equipment capable of intercepting and analysing radio and other electronic communications. bbc.com

Pictured below is the interior layout of the EH-3 Aries: