NORTH PLAINFIELD — Route 22 was shut in both directions in North Plainfield late last night as firefighters fought a persistent blaze in a commercial building.

Flames shot from a window and roof of the Camp-Out trailer dealership at the highway’s intersection with Jefferson Avenue shortly after 10 p.m., said North Plainfield police spokesman Sgt. Brian Rosko.

The highway was completely closed about 11:15 p.m. as the fire grew, although at the time there seemed little risk of it spreading to a nearby used-car dealership, Rosko said.

Fire companies from North Plainfield and surrounding towns, including Watchung and Green Brook, helped fight the fire, he said.

The cause of the fire has yet to be determined, he said.