By JEREMY PAGE

BEIJING—The Chinese government has asked Cambodia to extradite to China a French architect with close ties to the wife of the ousted Communist Party official Bo Xilai, said Cambodia's deputy national police chief.

Beijing requested the extradition of Patrick Henri Devillers last week because it suspected him of involvement in the scandal that brought down Mr. Bo, Cambodia's deputy national police commissioner, Sok Phal, told The Wall Street Journal.

"We don't know yet how to deal with him because the situation is changing all the time. We are now investigating the case more," Mr. Sok said. "We may extradite him to China due to the agreement between the two countries."

The Chinese Foreign Ministry said it had no information on the matter.

France's Foreign Ministry declined to comment on whether China was trying to extradite Mr. Devillers, but said it was following his case closely and that no charges should be brought against him without a proper legal basis.

The Frenchman used to live in China and according to people who knew him there had close ties to Mr. Bo's wife, Gu Kailai, who the Chinese government says is a murder suspect in the death in China last year of Neil Heywood, a British business consultant. Ms. Gu hasn't commented on the allegations.

Messrs. Devillers and Heywood were both part of a small circle of friends and advisers around Ms. Gu in the northeastern city of Dalian in the 1990s, when Mr. Bo was mayor there.

The Frenchman also shared a residential address with her in the southern British city of Bournemouth between 2000 and 2003, according to British public records.

It is extremely rare for any country to extradite a citizen of a European Union nation to China.

Bernard Valero, a French foreign ministry spokesman, said French authorities had been told Mr. Devillers, a resident of Cambodia, was arrested on June 13.

"We're very closely following this case, making sure he has consular protection. The consul visited him immediately after his arrest and keeps visiting him every day since," he said.

"We have asked the Cambodian authorities clarification on the motives for his arrest. We also expressed our vigilance that no charge of any sort can be pressed against him if the juridical basis isn't clearly established."

Cambodia is a major recipient of Chinese economic aid and investment, and Mr. Devillers' arrest coincided with a visit last week by He Guoqiang, the Chinese leader overseeing the probe of the Bo case.

Cambodia, which has an extradition treaty with China, attracted international criticism in 2009 when it deported to China 20 Chinese asylum seekers from the mostly Muslim Uighur ethnic minority, which mainly inhabits the northwestern region of Xinjiang.
—Sun Narin in Phnom Penh and Geraldine Amiel in Paris contributed to this article.

Write to Jeremy Page at jeremy.page@wsj.com

A version of this article appeared June 21, 2012, on page A13 in the U.S. edition of The Wall Street Journal, with the headline: China Makes Plea For Extradition.