TEMECULA —— One student suffered serious burns Friday and two others were injured when an explosion occurred in a biology classroom, authorities said.

The 10:44 a.m. explosion took place during a college-preparatory course in a classroom in the 700 building, a spokeswoman for the district said. Students in that building were evacuated, however classes throughout the rest of the campus are continuing, district officials said.

The male student who was most seriously injured suffered burns and cuts to his face and was flown by medical helicopter to Arrowhead Regional Medical Center in San Bernardino.

The two other students, a male and a female, were taken to Inland Valley Medical Center in Wildomar for treatment of minor to moderate injuries, authorities said.

About 40 freshmen and sophomores were in the class when the explosion happened, but the rest were not injured, district officials said. The other students who were in the class at the time were being decontaminated by Hazardous Materials Team officers, Temecula's Deputy Fire Marshal Jason Neuman said. That process included showering in the gymnasium, he added.

District officials did not release the name of the teacher in the class, nor what the students were working on at the time of the explosion.