An explosion Monday morning struck a house that was under construction in East Bethel and injured three workers who were freed from the rubble by rescuers, officials said.

The Anoka County Sheriff's Office said the blast occurred shortly before 8:30 a.m. at property in the 2800 block of Viking Boulevard NE. near Greenbrook Drive NE.

Once the rescue crew pulled the men from the debris, two were taken by ground ambulance and one by helicopter to HCMC in downtown Minneapolis, said Sheriff's Lt. Bill Jacobson.

Jacobson said midafternoon Monday that he had no information about the victims' conditions, and he did not release their identities other than to say they were workingfor a contractor.

Officials have yet to offer a preliminary cause for the explosion.

John Buchta said he was working at the East Bethel Auto Body on Viking Boulevard, when the shop shook hard from the blast across the street.

"We were sitting in the office about 8:27 and it sounded like the shop blew up," said Buchta, who works across the street from the scene of the explosion. "I ran outside and saw no smoke, but I could smell something a little bit."

Buchta said he saw law enforcement squad vehicles, a helicopter and at least one ground ambulance converging on the scene.

The explosion was big enough, he said, that "I got calls from Andover wondering what happened."