The fire was reported at about 1 a.m. in a four-unit apartment building at 1309 Fillmore St.
Residents told police that they had seen 26-year-old Tamisha Walker breaking the windows to apartment 3, from which she had been evicted a week ago, Bays said.
She eventually kicked in the door and went in, Bays said.
Witnesses also allegedly heard Walker "make some statements that she was going to burn the place down," Bays said.
After Walker left, residents went to check on the apartment and found two separate fires inside the unit.
Balled-up towels were found on the stove next to the burners, which were on high, and a mattress had been set on fire in the back bedroom, Bays said.
One of the residents was able to turn the stove off and partially contain the fire in the kitchen, but the mattress was fully engulfed in flames.
While residents were dealing with the fire, a 12-year-old boy who had gone downstairs with them to check on the apartment ran back upstairs and started banging on people's doors and shouting that there was a fire. Several people had been asleep and were awakened by the boy, Bays said.
A total of 10 residents were safely evacuated from the building, Bays said.
The boy, along with other residents, identified Walker as the alleged arsonist and several of them knew where she was staying.
Police found Walker hiding in a bedroom closet under some clothes, Bays said.
She allegedly denied any involvement in the fire, but was arrested and booked into county jail on suspicion of arson, burglary and an outstanding warrant, Bays said.
Police plan to present the case to the Contra Costa County District Attorney's office today. Bays said prosecutors could decide to charge Walker with additional charges, including assault, in connection with the incident.
She is being held at county jail in lieu of $300,000 bail.
The American Red Cross is helping the displaced residents.
