A slow-moving forest fire scorched about five acres near Mount Laguna today, authorities reported.

Several area residents made emergency calls about 4 a.m. to report seeing smoke from the blaze, which erupted about a mile west of Laguna Meadows campground, according to the U.S. Forest Service.

Firefighters had to hike in to the remote area, USFS spokesman Brian Harris said. Aircraft crews with Cal Fire and the city of San Diego prepared to assist and remained on standby through the morning but turned out not to be needed, he said.

By noon, the contingent of 58 federal personnel had fully contained the "low-intensity fire," which mostly burned grass and natural forest debris underneath stands of pine and oak trees, according to Harris.

The flames were never an immediate threat to structures.

The precise cause of the blaze was under investigation, though it was "certainly" of human origin, possibly sparked by the embers of a campfire, the spokesman said.