An explosion the morning of April 1 at a business in the Allen Drive commercial complex on Route 7 in Gaylordsville happened when the business owner opened a garage door to the building, New Milford fire officials said.

The business owner, Greg Lee, 50, of Roxbury, smelled propane when he arrived to work at 7:45 a.m.

As he hit the button to open the electric garage door, a spark set off the blast.

Within seconds, the large, metal-framed building was demolished. Only the frame remained. The blast was heard for miles away and left windows blown out of neighboring homes and Alfredo's Restaurant next door damaged.

Seriously burned when the building exploded, Mr. Lee walked around looking for his dog, Zoey. The Roxbury resident was soon transported to Danbury Hospital with second-degree burns and quickly transferred to Bridgeport Hospital's burn unit -- but not before Zoey was found hiding in a nearby shed.

Mr. Lee was listed in good condition Wednesday according to Bridgeport Hospital public relations officer John Cappiello.

Zoey survived with singed fur and a burned area around one eye, said Christina Monti, Mr. Lee's stepdaughter.

"I'm sure the building was full of propane," said Gaylordsville fire chief Lee Hendrix. "There wasn't much fire at all when we arrived. The only fire was in the back of the building when I arrived."

Fire arshal Karen Facey said the explosion had been caused by propane but the exact site of the leak had not been identified by her as of Wednesday.

A forensic study is being conducted of all propane sources at the site, she said. She hopes to interview Mr. Lee next week.

Kevin Hart, the owner of the building, said last week he hadn't decided if he would rebuild.