Peter Humphrey and his wife, Yu Yingzeng, were detained in Shanghai on July 10 as police probed bribery allegations against British drugmaker GlaxoSmithKline (GSK).
In China, an arrest typically means police believe they have enough evidence for a case to be brought to trial. Detentions can last for weeks and end in release without charges being filed.
It was not immediately clear if Humphrey's arrest was directly related to the investigation of GSK, which has been accused by China of funneling up to 3 billion yuan ($489 million) to travel agencies to facilitate bribes to doctors and officials.
China has taken a tough stance on corruption and high prices in the pharmaceutical industry as it unrolls wider healthcare access and faces an estimated $1 trillion healthcare bill by 2020.
"We can confirm the arrest of a British national, Peter Humphrey, in Shanghai on Monday the 19th of August. We are currently providing consular assistance," British Embassy spokeswoman Hannah Oussedik told Reuters by phone.
Oussedik declined to offer additional information about the reasons for Humphrey's arrest. The U.S. Embassy in Beijing could not be reached immediately to confirm whether Yu was also arrested. The U.S. Consulate in Shanghai declined to comment.
Shanghai police did not respond to a request for comment.
A statement issued by a member of Humphrey's family said both Humphrey and Yu had been arrested.
A source close to the family said they had not yet been told which charges would be laid against Humphrey, or when, but the statement said lawyers told the family the couple had been detained last month because they broke a law related to buying private information.
Humphrey and Yu co-founded ChinaWhys, a business risk advisory firm that has done work with drugs companies, including GSK, separate sources familiar with the matter have said.
Humphrey worked as a journalist for Reuters in the 1980s and 90s. The ChinaWhys website says he has been a risk management specialist and corporate detective for 14 years.
In March 2010, four executives from mining giant Rio Tinto were jailed for taking bribes and stealing commercial secrets. Three of those executives were Chinese while the fourth was a Chinese-born Australian.
(Reporting by Michael Martina, Megha Rajagopalan, Hui Li and Shanghai newsroom; Editing by Kazunori Takada and Nick Macfie)