State: Explosion at chemical company was accidental

LEOMINSTER, Mass. -- A chemical explosion that blew the roof off a small pharmaceutical research lab here last week was accidental, state investigators said Monday.

The blast at Polycarbon Industries Inc. took place during research operations on March 22. One worker suffered a minor burn to his hand and nine nearby homes were evacuated.

"There was no intentional act behind this explosion," state fire Marshal Stephen D. Coan said at a news conference at Leominster City Hall on Monday.

Coan said the building suffered significant structural damage, which delayed investigators from getting inside.