SUN PRAIRIE, Wis. — An explosion rocked the downtown area of a suburb of Madison, Wisconsin, after a contractor struck a natural gas main Tuesday, injuring at least two firefighters and a police officer, authorities said.

No deaths were immediately reported, and it wasn’t known if anyone else was hurt.

Police Lt. Kevin Konopacki said that around 6:20 p.m., firefighters and police responded to a reported gas leak in downtown Sun Prairie, a community of about 30,000. Witnesses reported the powerful blast about 7:15 p.m. It sent a plume of smoke and flames into the air.

Konopacki said the firefighters and officer were taken to a hospital. He said he didn’t know if anyone else was hurt.

WE Energies spokeswoman Cathy Schulze said the gas main strike was reported to the utility early Tuesday evening ahead of the explosion. She said the utility’s first responders were in the area working to shut off the flow of gas and make the area safe.

The blast appeared to be centered on the Barr House, a pub in an area filled with other bars, restaurants and businesses. Authorities evacuated a five-block radius and set up a shelter at Sun Prairie High School.

Steve Owen, 60, who owns Sun City Cyclery and Skates in downtown Sun Prairie, said he saw firefighters and police officers on the street and then the explosion happened. He said the building across from his shop “literally lifted up.”

He said the force of the blast knocked him back in his chair and that he ran outside and saw a ball of fire.

“People were scrambling,” said Owen, who lives above his shop.

Jill Thompson, 56, who lives about two blocks from where the blast occurred, said, “It shook the whole building. I thought someone had hit the building with their vehicle. We seen the smoke immediately.”

The area is about half a block from City Hall.