New Jersey ? An explosion leveled a house under construction and a vacant building next door early Friday in Irvington, killing one worker and injuring four others.

Authorities were investigating whether someone broke into the house and damaged a natural gas line.

The explosion was so powerful it caused debris to fly up to four blocks away and sparked several fires that were under control within two hours, Deputy Fire Chief Charles Weiss said. Emergency crews used search dogs and chain saws to rescue trapped construction workers from the smoking pile of splintered wood and siding.