Chinese authorities are considering charging seven men over the beating to death of a journalist at an illegal coal mine, state media has said.
The safety record of Chinese mines is poor
Lan Chengzhang, who worked for China Trade News, died of head injuries after visiting the Shanxi mine in January.
The incident drew national attention with President Hu Jintao calling for a swift investigation into the case.
Some local officials suggested Mr Lan was not an accredited journalist and may have been trying to extort money.
Lan's employers said he had only just begun working for the publication and had not yet completed his trial period.
According to the official People's Daily newspaper, police said the mine's owner, Hou Zhenrun, had concluded Lan was a bogus reporter because his documents lacked the certification seal of the State Press and Publication Administration.
Chang Hanwen, another journalist who accompanied Lan, accused the mine's boss of co-ordinating a group attack on them.
Lan died the day after the alleged attack, on 10 January, while Chang Hanwen suffered a broken right arm.
China's mines are among the most dangerous in the world, with nearly 5,000 workers losing their lives in accidents last year, many of them in unregulated operations.
The government is seeking to improve working conditions in the industry, which has historically been plagued by poor safety standards and a lack of proper equipment.
The case drew a rare intervention from President Hu and other senior government officials who called for it to be "rapidly investigated".
The death provoked an outcry from journalists working in China, where the media is tightly controlled, and foreign press groups.