Police have evacuated several buildings around a Palo Alto home where they say they have contained an "unstable subject."
Police said the home is in the 3400 block of Klamath Lane, a residential block near U.S. Highway 101 and San Antonio Road.
Officers have evacuated three nearby buildings, police said.
The incident, which a dispatcher said began several hours ago, has prompted street closures in the area.
Police have not yet released further details about the incident.