Police urged people near or downwind of an ice rink in Tewksbury, Massachusetts, to evacuate Tuesday afternoon because of "a hazardous condition" later identified as an ammonia leak.
They later said the leak at the Breakaway Ice Center on Carter Street was contained safely.
"All have been evacuated; no injuries reported," police said on Twitter.
A large police, firefighter and EMS response was at the scene Tuesday afternoon.
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There was an initial report of an explosion that actually turned out to be a gas tank pressure relief valve bursting, according to Tewksbury Fire Chief Joseph Kearns.
He said one person tried to stop the leak by hitting the emergency off button. That person was taken to the hospital for ammonia inhalation and is doing fine.
There were roughly 50 people inside the ice rink at the time, including a group of teens playing hockey. Everyone is safe, fire officials said.
The chief said the gas never leaked inside the venue, but rather outside, which is why nearby residents were evacuated.
"I could smell some of the ammonia," Don Willis, who was evacuated from his home said. He said the situation was stressful.
"I have two golden retrievers and they are my whole life. I have to make sure they are OK," he explained.
It wasn't immediately clear what caused the leak. Local firefighters were working with a hazardous materials team to investigate.
This developing story will be updated when more information is available.