BRISBANE -- A three-alarm grass fire burning on the eastern side of San Bruno Mountain in Brisbane is expected to be contained by 4 p.m., a North County Fire Authority spokesman said.

The flames were first reported around noon and threatened one home in the 3700 block of Bayshore Road, information officer Clyde Preston said. Around 7-acres of grassland have been charred, but the flames have not destroyed any structures.

Nineteen fire engines have responded to the flames, as well as a helicopter and two air tankers that are dropping water on the fire, Preston said. Officials estimate that the fire will be completely under control by 7 p.m.

The blaze burned up the hillside and shut down the Oyster Point off-ramps to U.S. Highway 101, California Highway Patrol Officer Kevin Kroncke said. A Sig-alert was issued at 1:04 p.m. and has not been canceled due to residual traffic as drivers slow down to view the flames.