SAN DIEGO – Fire crews doused a small brush fire Friday that ignited a palm tree off of state Route 163 near the Laurel Street Bridge, California Highway Patrol said.

The fire was reported just before 5 a.m. on the right-hand side of the freeway under the bridge, a CHP traffic incident log shows. About a half-dozen firefighters were seen putting out hot spots leftover from the morning blaze that left a large palm tree smoldering.

The tree, which is between 30 and 40 feet tall, is expected to throw off smoke “all day,” officers said.

The cause of the fire was not immediately clear, but firefighters say it may have been caused by someone throwing something from the bridge.

No further information was available.