SAN JOSE, Aug. 26 — The FBI, thwarted when an early-morning raid failed to net Manson cult follower Susan Murphy and a sister prison escapee, said yesterday investigators believe the two fugitives still are in the area.

Agents took a 27-year-old woman into custody and charged her with harboring a federal fugitive after the 7:30 a.m. raid on a downtown San Jose apartment. Pamela J. Bailey, whom the FBI said was on probation for a forgery conviction in Chicago, was held on $10,000 bail, and a preliminary hearing was set for today.

Miss Bailey was accused of harboring Diane Ellis, a 33-year-old convicted bank robber who escaped with Ms. Murphy 12 days ago from the Terminal Island federal prison in Los Angeles.

The pair overpowered and beat a female prison guard, fleeing in her car, and a day later rented another auto at San Francisco International Airport. The last confirmed sighting of Ms. Murphy was Aug. 16 at a Santa Cruz hospital, where the FBI said she was treated for an undisclosed ailment.

Ms. Murphy, 34, was serving a five-year sentence for conspiring with Sandra Good, another figure in the Charles Manson family, to mail threatening letters to businessmen they accused of polluting the environment.

“We had hopes of arresting at least Miss Ellis,” FBI spokesman Tony Triplett said. He said that agents raided the Bailey apartment after several persons identified photos of Miss Ellis as a woman they had seen entering the residence.

“We still believe they are in the area,” said Charles Bates, the FBI agent coordinating the search. He did not elaborate, but an FBI affidavit disclosed that a neighbor told investigators that Miss Ellis and another woman had been seen at the Bailey apartment last Sunday.

Miss Murphy lived in Sacramento with Miss Good and Lynette “Squeaky” Fromme, all professed followers of mass murderer Charles Manson. Miss Ellis, of San Jose, was serving time for parole violations on a bank robbery conviction.