STOCKHOLM/BEIJING, Oct 24 (Reuters) – A Swedish bookseller detained in China after publishing books on the personal lives of President Xi Jinping and other Communist Party leaders has been released, Chinese authorities said on Tuesday.

The whereabouts of Gui Minhai, a Chinese-born Swede, could not be confirmed, however, and he has yet to contact his family.

Gui was abducted in Thailand while on holiday in 2015, one of five Hong Kong booksellers who went missing that year and later appeared in mainland Chinese custody. The four others have returned to Hong Kong.

Chinese authorities say Gui was involved in a traffic accident in 2003, although that is questioned by his family.

“According to what we understand, because Gui Minhai has served his sentence for the crime of causing traffic accident casualties, he was released on Oct. 17,” the Chinese Foreign Ministry said in an e-mailed statement to Reuters.

The Swedish Foreign Ministry said it had been informed by its Chinese counterpart of Gui’s release and that it was working to confirm the information.

However, Gui’s family questioned if he really was free. His daughter said he had made no contact with her or any other relatives.

“Today it has been a week since October 17 and I still do not know where my father is,” Angela Gui said in a statement. “I am deeply concerned for his wellbeing.”

The report of Gui’s release coincides with the end of China’s 19th Communist Party congress which has further consolidated President Xi Jinping’s power.

Lam Wing-kee, one of the other four booksellers, told Reuters he did not know Gui’s whereabouts.

Lam said he feared the government of Xi would further erode the “one country, two systems” formula that is supposed to guarantee Hong Kong a large degree of autonomy under Chinese rule.

“He (Xi) will continue to tighten things (for Hong Kong). There will be no loosening,” he said.

Earlier this year, Gui won a prize for free speech and press freedom awarded by Swedish media organisation Publicistklubben. (Reporting by Johan Ahlander, additional reporting by Ben Blanchard in Beijing and James Pomfret in Hong Kong, editing by Niklas Pollard and Ed Osmond)