A Frenchman, who is believed to have close ties to disgraced Chinese politician Bo Xilai, has returned to China to help the investigation into the country's biggest political scandal in decades.
Patrick Henri Devillers, who is 52, was detained last month in Cambodia, where he had been living for several years. He was held at the behest of China because of his suspected business links to Gu Kailai - the wife of deposed Chinese politician Bo Xilai.
Information Minister Khieu Kanharith told reporters that Devillers, an architect, had taken a flight from Cambodia to China late on Tuesday and that he had left of his own free will, without an escort from the French embassy.
"He voluntarily went as a witness," he said, adding that China had given an assurance that Devillers would only be required for up to 60 days before being allowed to return.
Bo's wife, Gu Kailai, has been named by China as a suspect in the murder last November of British businessman Neil Heywood. Both Heywood and Devillers were known to be close to her.
Devillers has lived in Cambodia for at least five years, according to friends. He entered Bo's inner circle while living in Dalian in the 1990s when Bo, who was mayor of the city at the time, helped him to chase up an unpaid debt.
China has not said publicly whether Devillers himself is accused of any crime. Bo was stripped of his post as Communist Party secretary of Chongqing in southwest China in March.
Cambodia is a close ally of China, which is a big aid donor and investor in the Southeast Asian country.
Bo, the former leader of the southwestern Chinese megacity of Chongqing, is being probed for corruption while his wife Gu has been detained for suspected involvement in the murder of British businessman Neil Heywood last year.
Mr Heywood was found dead in a hotel in Chongqing on 15 November 2011.
Local officials initially said he died of excessive drinking, but the government announced in April that it was investigating Mr Bo's wife in connection with the case.
Bo had been widely tipped for promotion to the top echelons of the Communist Party before the scandal spectacularly derailed his political career.
Devillers is believed to have first crossed paths with the former power couple in the 1990s, when Bo hired him to do some architectural work in the Chinese city of Dalian.