An explosion leveled two homes early Friday, killing one construction worker and injuring at least four more, authorities said.

Emergency workers used search dogs and chain saws to pick over a smoking pile of splintered wood and siding, scrambling to find people.

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"There's still people trapped inside the pile of debris," Deputy Fire Chief Charles Weiss said.

The explosion around 7:30 a.m. involved a vacant six-family house and a new three-story home that was under construction, said Paul Loriquet, spokesman for the Essex County prosecutor's office.

Natural gas was considered a likely cause of the explosion.

"There was a strong gas odor emanating from the location, so we believe gas could have been involved in the explosion," Loriquet said.

Weiss said the explosion caused debris to fly up to four blocks away and sparked several fires, which were under control within two hours.

Of the four injured, only one needed to be hospitalized, Weiss said.

The explosion happened in a neighborhood in Irvington, about 5 miles west of Newark.

John Buniewicz, 72, who lives a half a block away, spilled hot coffee on his kitchen floor as he heard the loud boom.

"It was so loud, I thought the roof came down, and I heard glass shattering all over the place," Buniewicz said.