HOLLISTON, MASS. (WHDH) - Two people were taken to the hospital by helicopter on Monday after an explosion inside a home in Holliston, police said. 

Police said emergency crews responded to the home on Westfield Drive shortly before 4 p.m. after a neighbor called 911.

On scene, police said first responders determined the two people, aged 59 and 61, “needed immediate medical attention.”

One woman speaking with 7NEWS said she first heard a boom around 4 p.m. and ran outside to find her neighbor coming out of his home with a friend and asking her to call 911.

The woman, Kristen Mahoney, said she called 911 and tried to help the two men on her lawn while they waited for first responders to arrive.

“It was a very sad incident because he’s my neighbor and I didn’t want anything bad to happen to them but they were both in shock,” Mahoney said. 

Speaking on scene, Holliston Fire Chief Michael Cassidy said the two men who were hurt each had burns to more than a third of their body.

“It’s awful,” one woman in the area said. “It’s tragic.”

Cassidy said there was damage in the basement as well as damage on the home’s first floor.

“There was a lot of charred paperwork and equipment that one would expect to find in a basement that had some melting from a flash fire,” he said.

The cause of the explosion remained under investigation as of Monday. Cassidy said a storm came through the area on Friday, though, causing trouble for electrical systems in some homes. 

Cassidy said the homeowner and the second person were working near the home’s boiler when the explosion happened. 

“I can tell that they were troubleshooting an issue with HVAC equipment in the basement,” he said. “There was an electrician and the homeowner that were in the basement at the time of the incident.”

Building and electrical inspectors, along with Eversource personnel, visited the site of this explosion on Monday. 

Electricity had been turned off to the home as of around 9 p.m.

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