A magnitude-5.3 earthquake struck Thursday afternoon under the ocean off Southern California and was felt widely along the mainland coast, but there were no immediate reports of damage or a tsunami warning.

The U.S. Geological Survey said the quake occurred at 12:29 p.m. in the Channel Islands region, about 38 miles (61 kilometers) southwest of the mainland city of Ventura.

Authorities in Los Angeles and Ventura counties did not report any immediate damage.

The Los Angeles Fire Department said it went into "earthquake mode" and firefighters from all 106 of its firehouses began surveys of their territories, including bridges, dams, large buildings and power lines.

"We currently have no reports of damage or injuries," fire department spokeswoman Margaret Stewart said.

The quake occurred at a depth of 10.5 miles (16.8 kilometers) and the epicenter was closest — 17 miles (27 kilometers) — to Santa Cruz Islands, which is part of Channel Islands National Park.

The island is largely unpopulated but does have some research facilities, historic buildings and hosts campers.