Authorities were able to begin an evacuation immediately after the leak was reported.
One firefighter was killed and several others were hurt in an explosion that happened downtown Sun Prairie on Tuesday. The blast destroyed several buildings and ignited a fire that belched a plume of ink-black smoke that could be seen for miles.
Cory Barr, age 34, was reported to have died in the July 10 blast that demolished Barr House, 100.
Dane County Sheriff's Department operations manager Paul Logan says people were hurt in the explosion Tuesday evening in Sun Prairie, which has about 30,000 people. Hundreds of residents were displaced from their home and found shelter at area schools and churches.
Sun Prairie is a suburb of the state capital of Madison. Police blocked off downtown streets from traffic and onlookers.
Officials with WE Energies told WISC in Madison, Wisconsin they have been made aware of a contractor hitting a natural gas main in downtown Sun Prairie.
WE Energies spokeswoman Cathy Schulze says the utility's first responders are in downtown Sun Prairie working to shut off the flow of gas and make the area safe.
"I always looked up to him and admired him because I feel like it takes a special kind of person to be on a fire department and be running in toward something that everyone else was running away from", she said.
The blast appeared to be centered on the Barr House, a pub in an area filled with other bars, restaurants and businesses.
"People were scrambling", said Owen, who lives above his shop.
He said the building across from his shop 'literally lifted up'.
Jill Thompson, 56, who lives about two blocks from where the blast occurred, said, "It shook the whole building".
The area is about half a block from the town's city hall.