SAN CRISTOBAL DE LAS CASAS, Mexico - Three arrests have been made in the slaying of an activist opposed to a mine operated by a Calgary-based Blackfire Exploration Ltd.

A spokesman for the Attorney General of the Mexican state of Chiapas confirmed three men are being detained while investigators continue to speak with witnesses and gather evidence.

One person is accused of the shooting and the other two are accused of being accomplices, Hector Flores of the Attorney General's office said from the state capital, Tuxtla Gutierrez.

Mariano Abarca Roblero, 51, was shot in front of his home on Nov. 27.

The local businessman and community leader was well known in Chiapas as a vocal opponent of the barite mine owned by Blackfire Exploration Ltd, which operates in Mexico through a subsidiary in a small town near the Guatemalan border.

Abarca Roblero accused the mine of harming the environment and creating conflict and division within his community.

Flores, the spokesman for the Attorney General's office, said authorities are looking into allegations two of the men worked for the company.

"Some have said -- and this is what we're still confirming -- that (the accused) worked directly or indirectly for the company," Flores said, adding that they received information one of the accused was a driver for Blackfire.

"For the moment we don't have any more information because the investigation is still ongoing," Flores said.

A news release from Blackfire said one of those arrested stopped working for the company June 6, 2008.

A spokesman couldn't immediately say what job he did at the company and why his employment ended.

"We will continue to operate normally while contributing to the region's social and economic development," said the release, calling Roblero's death a "regretful crime."

The spokesman, who did not want his name used, said the company was not involved in Roblero's death in any way and couldn't know what its employees did outside of their hours at work.

"To this hour Blackfire Exploration Mexico or its legal representation hasn't been officially contacted by the state authorities," he wrote in an email from Mexico on Monday afternoon. "We will co-operate fully if this happens."

The company will not pay for the defence of any employees involved in criminal activities, he said.

The family of the slain activist, along with a coalition of anti-mining organizations, have asked to meet Wednesday with Gov. Gen. Michaelle Jean, who is visiting Mexico. But the family said Monday there had been no response to the request.

Last week a demonstration was held in front of Canada's embassy in Mexico City over the shooting as well as the activities of Canadian mining companies

The son of the slain activist said he and his family now have 24-hour police protection and are afraid to go out.