A New Hampshire high school is on lockdown after a meth lab exploded nearby during a raid and ignited a large fire.

Franklin Police Chief David Goldstein tells The Citizen newspaper there was an explosion and fire minutes after police entered the building Tuesday morning. He says two men and one woman were arrested.

School Superintendent Jo Ellen Divoli tells The Associated Press that police requested the lockdown at Franklin High School. The house is less than a tenth of a mile from the school.

She says students are in their classrooms with their teachers. The school has more than 400 students in grades nine through 12.