Fire crews spent the night watching for hot spots in a brush fire that broke out in Sorrento Valley over the weekend and grew to 138 acres and was 91% contained Thursday.
Fire crews planned to continue clearing lines of vegetation to contain the fire after daylight.
One evacuation order remained in place in the fire zone.
The fire started at about 1:30 p.m. Sunday in the Peñasquitos Creek area east of Interstate 15, with staging at Sorrento Valley Boulevard and Vista Sorrento Parkway, according to radio traffic. An aerial attack got underway immediately.
The fire burned slowly in medium fuel, but firefighters planned for structure protection as a precaution, the San Diego Fire-Rescue Department reported.
Flames consumed about 20 to 25 acres within 90 minutes, and eventually grew to more than 130 acres, prompting the evacuation order, fire officials said. No structural damage or injuries have been reported.
Brandon James Glasgo, 30, was arrested on suspicion of arson after a resident spotted him walking out of an open, brushy area in the 10800 block of Vista Sorrento Parkway as the flames began spreading, according to police.
He was formally charged with one felony arson count, which led to Wednesday's arraignment, where Deputy District Attorney Jacob Carbajal said Glasgo admitted to police that he started the fire.
Glasgo allegedly told investigators that he got into an altercation with a bicyclist along the trail, which angered him and led him to set fire to a large tumbleweed, the prosecutor said.
He later apologized for setting the fire, though Carbajal claimed he laughed and said he maybe should have tried stamping the fire out after being told it had grown to more than 130 acres.
Glasgo later allegedly pointed out the fire's origin point on a map, which Carbajal said matched the spot investigators determined to be the location where the fire started.
Glasgo pleaded not guilty Wednesday to a felony arson count.
He was being held in lieu of $75,000 bail. If released, he must abide by conditions that include GPS monitoring and a prohibition against possessing incendiary devices.
There was no indication on the San Diego County Sheriff's Office website that Glasgo had been released.
The arson count carries a maximum possible sentence of six years in state prison.
