A woman and five children were hospitalized for carbon monoxide intoxication yesterday due to a ventilation issue in a Waltham laundromat, fire officials said.

First responders found the parties had elevated carbon monoxide readings after being inside the laundromat at 85 River St., Deputy Chief Andrew Mullin said.

They were transported for treatment to a local hospital.

There was no immediate information available on their conditions last night, Mullin said.

Firefighters shut down the gas supply to all of the laundromat’s heaters and dryers and ventilated the building and tried to determine the source of the problem, Mullin said.