Nobel Prize jurors who accepted all-expenses-paid trips to China to discuss the coveted awards are being investigated on suspicion of bribery, a Swedish prosecutor said Thursday.

Anti-corruption prosecutor Nils-Erik Schultz said he opened the probe to determine whether the trips in 2006 and 2008 were meant to influence the decisions of the Nobel committees. He declined to name the jurors or say how many were being investigated.

The probe was prompted by a Swedish Radio report that said three jurors from the medicine, chemistry and physics committees were invited to China to explain the selection process and what it takes to win a Nobel Prize. Chinese authorities paid for their plane tickets, hotels and meals, the report said.

If charged and convicted, the jurors would face fines or up to two years in prison. However, Swedish prosecutors often drop preliminary investigations without pressing charges.

Gunnar Oquist, the permanent secretary of the Royal Swedish Academy of Sciences, which awards the Nobels in chemistry and physics and the related Bank of Sweden Nobel memorial prize in economics, acknowledged that the trips were inappropriate.

"We should be very careful not to put ourselves in a situation where the Nobel committee's work can be called into question," he told the Associated Press by phone. "I think we should have thought about that here."

Oquist said he hoped the case would not affect the reputation of the annual Nobel Prizes, which honour groundbreaking achievements in medicine, physics, chemistry, literature and peace. Five Europeans, four Americans and three Japanese formally received the 2008 awards in a ceremony last week.

"I think that if we had known that the Nobel Prize would be at the centre of this trip, we probably would have discouraged our members from going," he added.

The last time China claimed a science prize was in 1957, when two Chinese researchers won the physics award, according to the Nobel website.

In Beijing, Foreign Ministry spokesman Liu Jianchao told reporters on Thursday he had no information about the case. "I'm not aware of this," Liu said.

The Nobels, worth $1.6 million each, are handed out every year on Dec. 10 to mark the anniversary of prize founder Alfred Nobel's death in 1896.