US authorities will probe British drugmaker GlaxoSmithKline's business practices in China in a bid to determine whether the company breached US anti-bribery laws.

The US Department of Justice (DoJ), which has been probing GSK's sales practices in several countries, has extended its investigation to the firm's China unit, reported Reuters, citing anonymous sources.

Pursued by Reuters, a GSK spokesman confirmed that the DoJ was investigating the company in China.

David Mawdsley, a spokesman for GSK in London said: "Since the investigation in China began, we have proactively reached out to relevant regulators. This includes the DoJ, and we have been in an ongoing dialogue with them."

GSK has been facing investigation in China into alleged malpractice by its executives.

The US Justice Department hopes to ascertain whether GSK, and other drugmakers, contravened the US Foreign Corrupt Practices Act, which prohibits American companies from resorting to bribery while doing business outside the US.

US authorities have jurisdiction over GSK, a British company, given that the drugmaker's stocks (American depository receipts) are traded on the New York Stock Exchange.

Earlier, Chinese police investigating GSK for alleged bribery and tax violations reportedly found that the crimes were organised by the company itself rather than individual staff members.

The official Xinhua news agency reported that Chinese police have revealed further details about the case after questioning more individuals. More people admitted to the "suspected transgressions", according to the news agency.

Earlier in the year, China's Ministry of Public Security accused unnamed GSK executives of routing 3bn yuan (£324m, €375m, $489m) in bribes to doctors through 700 travel agencies and consultancies over six years.

GSK admitted that some Chinese executives appeared to have broken the law, but CEO Andrew Witty said that their head office had no prior knowledge about the wrongdoing.

In a bid to repair its tainted image in connection with the scandal, the company appointed Herve Gisserot, senior vice-president for Europe, as the new chief of its China operations.

He replaced Mark Reilly.

Other foreign firms facing bribery allegations in China include French drugmaker Sanofi, Switzerland's Novartis and US drug giant Eli Lilly.