British investigator Peter Humphrey, who was sentenced to two and a half years in jail for illegally obtaining private citizen's information, in China, has been released seven months earlier than scheduled.

The status of his American wife, Yu Yingzeng, who was given a two year sentence and due to be released in July, is not known, news agency AFP reported, quoting a family friend and his son Harvey Humphrey. Yu was also Humphrey's partner in their investigative firm, ChinaWhys.

According to AFP, Humphrey and his wife were hired by GSK to investigate the source of a sex tape involving the company's boss in China, shortly before the multinational became embroiled in bribery allegations in the country.

"He [Humphrey] was notified today that the court decided to reduce his sentence by seven months," the unidentified family friend said, adding that Humphrey was scheduled to be released in January 2016.

"The British consulate is preparing an emergency passport and then he will be deported" she said.

A spokesman for the British consulate in Shanghai has confirmed that a British national has been released from custody and said it was providing assistance, according to AFP.

Humphrey being tested for cancer

The friend added that Humphrey is currently in hospital, where he has been for several weeks, undergoing medical tests for a potentially serious form of cancer.

Humphrey's son, Harvey, in a statement to AFP, said: "I am stunned and delighted and I hope to see both my parents as soon as possible. My father may need treatment for his health but he will soon be able to speak for himself."

According to the Financial Times, Humphrey and Yu were detained for more than a year before their sentencing last August.

GSK was fined $490m (£318.55m) by a court in China after it was found guilty of bribing doctors and hospitals to have their products promoted. In addition, GSK's former head of China operations, Mark Reilly was handed a three year suspended prison sentence and was deported.

Other GSK executives were also given suspended jail sentences.