Autopsies were begun on seven bodies found buried in shallow graves in a rooming house yard as authorities searched for the landlady suspected of killing her tenants.

Workers with shovels and tractors Tuesday finished digging up the yard where the bodies have been found since Friday, and began excavating adjacent land where the landlady reportedly gardened.Police Sgt. Bob Burns said no additional bodies were unearthed during a search of the rooming house Tuesday.

Burns said police suspect the victims, all believed to be elderly, were killed for their Social Security checks. The first of the autopsies, to determine the cause of death and identities, is under way at the coroner's office, he added.

The FBI has joined the search for the 59-year-old landlady, Dorothea Montalvo Puente, which has focused on Las Vegas, Burns said. An arrest warrant charging her with murder was issued Monday.

"She may have gone to see a relative in Las Vegas. We are investigating that. The Las Vegas police have not completed their investigation."

A Sacramento television station KCRA reported that Puente's nephew, Michael Montalvo, told Las Vegas police he picked up Puente at the airport Monday morning.

Both Burns and Las Vegas police declined comment on that report, but Las Vegas Metropolitan Police Detective Augie Knudson said his department had issued an all-points bulletin for Puente.