OSAKA -- Four men were injured Monday morning when a fire gutted a closed-down historic kabuki theater in a main entertainment district here, police said.

Two of the men were working to raze the run-down Nakaza theater in the Dotonbori district when an explosion occurred around 3:10 a.m., triggering a fire. The other two men are firefighters.

The blaze, which took firefighters five hours to put out, gutted the theater and damaged more than a dozen buildings in the neighborhood, mostly bars and eateries.