The investigation of the owner of a martial arts gymnasium here arrested for the brutal beating of a woman is being expanded after police found human bones at the facility, Spanish authorities said Monday.

Juan Carlos Aguilar, 47, was arrested Sunday for putting a 29-year-old Nigerian prostitute into a coma and now police are looking into his possible involvement in other crimes.

He confessed on Monday that last week he murdered a woman, sources close to the investigation told EFE.

The Basque regional police arrested Aguilar on Sunday at his gym in Bilbao, where he was found with a woman who had been brutally attacked and had her hands, feet and neck bound.

After the arrest, police searched the gym and found skeletal remains, which are now being examined, and sources involved with the investigation said that the indications are that they are human.

Police had been called by a witness who early Sunday afternoon had seen a woman being forced into the gym.

Investigators on Monday also looked for remains in the Bilbao estuary and searched Aguilar's home and gym, and they also examined other places where he had been over the past few hours in an effort to turn up evidence that would help them in the case.

Aguilar has a police record but those events have "nothing to do with this type of deed," a source said. EFE