COOPERSBURG (AP) - The explosion of two tractor-trailers filled with fireworks in eastern Pennsylvania, killing one person and injuring another, is under investigation, officials said Wednesday.

The Lehigh County coroner said 50-year-old Brian Ehret of Zionsville in Lower Milford Township was pronounced dead in the backyard of his home after the series of blasts just before 3 p.m. Tuesday. An autopsy is scheduled Thursday to determine the cause and manner of death.

Alcohol, Tobacco, Firearms and Explosives agents joined state investigators at the scene to comb through the trailers and a building that were destroyed.

The blasts drew neighbors and passersby.

A.J. Molaee told WPVI-TV he and his parents aided a man lying on the ground.

“He said, ‘My friend Brian’s in there in the trailer and my dog, is my dog OK? And I’m gonna die, I’m gonna die,’” Molaee recalled. “We’re asking him what happened? He said, ‘I just walked in and the whole place exploded.’”

Neighbors reported the blasts shook their homes and black smoke rose from the scene.