Chinese authorities on Wednesday deported a British investigator and his wife linked to a corruption case involving pharmaceutical giant GlaxoSmithKline (GSK), after releasing them from jail over a week ago, family sources told AFP.

British national Peter Humphrey and his wife Yu Yingzeng, a naturalised US citizen, had departed on a flight to London from Shanghai, their son and a family friend said. The couple had served time for illegally obtaining the personal information of Chinese citizens.

"Peter and Ying are on the Virgin flight to London," said the friend, who declined to be named.

The Shanghai office of Virgin Atlantic Airways said the flight to London had a scheduled departure of around 1140 am (0340 GMT) local time.

"I am extremely glad that this ordeal will be over by this afternoon," their son, Harvey Humphrey, said in a statement provided to AFP.

The couple ran an investigative firm, ChinaWhys, which was hired by GSK to probe a sex tape of the company's then China boss and other issues shortly before the British pharmaceutical company itself became the target of a Chinese government investigation into bribery allegations.

Humphrey, who is suffering from health problems, was released seven months early after being sentenced to two-and-a-half years in prison by a Shanghai court in August last year. Time served in detention was counted towards the jail term.

Yu was freed a month early after serving nearly all of her two-year term.

A spokesman for the British Consulate in Shanghai confirmed that Humphrey had been deported while the US Consulate in the city did not immediately respond to request for comment on Yu's case.

Humphrey is expected to seek medical care after he returns to Britain, the family friend said. He had previously undergone tests for an unspecified cancer while being held in Shanghai.

GSK was fined 3.0 billion yuan ($490 million) by a Chinese court last September following a nearly year-long bribery probe.

The court ordered the firm's former head of China operations, Mark Reilly, to be deported, and sentenced four other former GSK executives to between two and four years in prison, state media have reported.