VANCOUVER, Wash. -- An Evergreen High School student and two staff members were injured Tuesday when an explosive device went off at the school, authorities said.

Police photo

The fireworks that triggered the small explosion.

Firefighters and police responded to the school's freshman academy at 1:53 p.m. Tuesday.

A senior student in a staff area had disassembled a small, snap-type firecracker and put it into his backpack.

Later, a staff member set the backpack down on a table and the impact triggered a small explosion, according to school officials.

Two high school staff members who reported dizziness and asked for medical assistance were taken to a hospital. They suffered minor injuries and took sick days on Wednesday.

The student also suffered minor injuries and was not transported to the hospital. School officials said Wednesday that the student had been "emergency expelled."

Classes were not canceled.