A "serious quarrel" between Huang Wenyi and his wife may have led to the mass murder of five members of the family and an employee, local police said on Friday.

Liu Xiaoping, a police officer in Foshan of South China's Guangdong Province, told media that Huang, 34, was officially detained in custody on Friday on suspicion of killing five members of his family and one of his employees on December 28 last year.

The press conference was the first news of the case since Huang's arrest on January 1 in Guangzhou, capital of Guangdong Province.

Speculation has been rife as to the circumstances surrounding the mass murder. It is alleged that Huang committed the murders after he discovered that he was not the father of his 7-year-old son, one of the six victims.

"So far, Huang has not confirmed this speculation during interrogation. We are still searching for the real cause of the murder," Liu said.

According to Liu, Huang has been "depressed" and may be suffering from a mental illness.

"He has told us little except that he quarrelled with his wife on the day of the murder," Liu said.

But Huang confessed to the murders on the day of his arrest, according to Liu.

Meanwhile, the local public security authority awarded 100,000 yuan ($12,500) to a member of the public who gave information to police that led to Huang's arrest.

Police began searching for Huang when he disappeared shortly after the murder.

Police discovered Huang in a small guesthouse in Guangzhou's Liwan District, close to Foshan.

Editor: Yan