Authorities Thursday said that someone set the $2-million fire that gutted an entire wing of classrooms at a San Gabriel high school last month.
The blaze March 20 destroyed two offices and 10 classrooms at Gabrielino High School, forcing students into makeshift classrooms ranging from the library to the boys' locker room.
More than 50 firefighters took two hours to extinguish the Saturday night blaze.
"We are saying the fire is of a suspicious origin that equates to arson," San Gabriel Fire Chief I.F. Sweet said. "We're requesting anyone with information to come forward."
Arson investigators from the San Gabriel and Alhambra fire departments along with agents from the federal Bureau of Alcohol, Tobacco and Firearms ruled out electrical, mechanical and accidental causes, Sweet said.
Sweet said the blaze was set inside the building at the southeastern corner.
"There were some signs and burn patterns that were abnormal. We don't know if it was adhesive from the carpet or a fuel," he said.
Although investigators have yet to get back laboratory results of suspicious materials found at the scene by ATF dogs, Sweet said, "the time of day and day of the week and other circumstances point to it being set."
Investigators said they are pursuing a number of leads and have interviewed students and staff who went to the school that Saturday, as well as the school's immediate neighbors.
"I hate to think anyone in the community could be responsible for burning down part of the school," said school board member Nancy Trask.
Gabrielino, using a converted middle school campus, opened five years ago as the San Gabriel Unified School District's first high school.
The blaze displaced about 400 of the school's 1,400 students from classrooms, forcing them to use the gym, the career center and just about any available space as classrooms.
On Monday, teachers began giving classes in 10 temporary portable classrooms in the student parking lot. Over spring break, the district plans to demolish the remaining charred timbers on the site to make way for more permanent classrooms this summer, Supt. Gary Goodson said.
Businesses, other school districts and former students have given financial help and provided replacement class materials and books, he said.
"One teacher lost 40 years of class materials," Goodson said. "Our kids have been terrific, our community outstanding. They've rallied around our teachers."