Swedish prosecutors have launched a preliminary investigation into possible bribery tarnishing the Nobel awards after revelations that members of three Swedish Nobel Committees received free trips to China from the Chinese government.

Earlier in December, Sveriges Radio reported that members of the three Nobel Committees for natural science - medicine, physics, and chemistry - travelled to China at the invitation of Beijing to speak about what it takes to receive a Nobel Prize, according to The Local, an English daily in Sweden.

Public prosecutor Nils-Erik Schultz has decided to probe the matter more closely to determine whether any of the Nobel representatives who accepted the paid trips to China could be charged with bribery.

'As of now [the investigation] isn’t directed at any particular person, but at a set of procedures. In the first instance we need to focus on a few trip to China,' Schultz is quoted as telling Sveriges Radio.

The trips took place in March 2006 and January 2008 and the Chinese government paid for the flights, hotels, and meals. One trip included two Nobel Committee representatives, while three representatives took part in the second trip.

Even the representatives themselves acknowledge that taking the trips was a risky endeavour.

'It’s a borderline case, but we discussed it ahead of time, but it is borderline,' said Bertil Fredholm, who heads the Karolinska Institutet Nobel Committee - charged with picking the winner of the Nobel Prize for Medicine.

Fredholm participated in one of the trips, but told Sveriges Radio he doubts that the trips would affect the impartiality of the committee in judging future Nobel nominees from China, The Local reported.

Sven Lidin of the Nobel Committee for Chemistry at the Royal Swedish Academy of Sciences, who also accepted a paid trip to China, expressed his doubts after the fact.

'Just the fact that you’re asking about this makes me think that it’s possible that it would have been a better idea to pay for it from Sweden,' he said.

Schultz’s investigation will determine whether or not to file bribery charges in the case.

'We have to figure out why someone decided that they wanted to pay for tickets and living expenses for these people; was there some thought that they would try to influence these people, who hold very important positions,' he said.

No Chinese citizen has won a Nobel Prize for the past three years.

Meanwhile, a second corruption case involves Anglo-Swedish pharmaceutical company AstraZeneca, which earlier this year signed a sponsor agreement with two Nobel companies with close ties to the Nobel Foundation: Nobel Web and Nobel Media.

Half of this year's Nobel Medicine Prize went to Harald zur Hausen of Germany for his discovery of the human papilloma virus (HPV) that causes cervical cancer.

AstraZeneca receives royalties for the two available vaccines against HPV.

Schultz said he was gathering information on the case to determine whether the pharmaceutical company had any influence over the Medicine Prize committee's choice of this year's winners.

However, he has not yet decided to formally launch a preliminary investigation.