Western High School, 4600 Falls Road, was closed today after a deliberately set fire sent heavy smoke through the building.

Capt. Patrick P. Flynn, spokesman for the city Fire Department, said the fire, ruled an arson, broke out in the basement janitorial supply room about 5:20 a.m.

Wooden shelves and janitorial supplies, including cardboard boxes, were burned. Flynn said fire damage, which was confined to the supply room, was estimated at $15,000. The fire was declared under control about 6 a.m.