CONCORD — A high school student who allegedly set fire to a wastebasket Monday at Concord High School has been caught, school district Superintendent Christine Rath said.

“We have identified the student who was responsible for this week's fire,” Rath said Tuesday night.

Rath said the student was a girl, but that she could not identify the student.

Concord High School officials locked down the school, which ordinarily has an open campus, on Tuesday while officials tried to find out who started the two fires in a bathroom at the school within the last week. Students were not permitted to walk the halls without a pass, she said.

Rath said another student came forward to identify the girl as the one who started Monday's fire.

“The high school administration did just what they needed to do,” Rath said. “The administration took it extremely seriously. They tried to send the message to students that this was extremely serious.”

Rath called the fires “a very uncommon occurrence.”

City Deputy Fire Chief Sean Toomey said the most recent fire happened Monday while school was in session. A student pulled a fire alarm after smelling smoke, he said.

Nobody was injured in either fire, both of which were started in and confined to trash cans in the bathroom, he said. However, he said, fire officials are concerned that such trash fires could burn plastic, releasing toxic fumes into the school.

“Our true concern here is safety,” Toomey said. “This time it was in a trash can, but could it get worse? Obviously, starting fires in a building occupied by 2,000 students is very serious.”

Toomey said the school is equipped with a sprinkler system, which was not activated by the relatively small fires.

Rath said officials will continue to investigate the matter to determine if the girl set the first fire or to catch who did.

Toomey said anyone with information is asked to call the city's fire prevention line at 225-8651 or anonymously at the Concord Crimeline, which is 226-3100.