BOSTON (CBS) – A gas main fire in Roslindale injured four utility workers Sunday night. The National Grid workers were working on a 10-inch natural gas line on Hyde Park Ave. at about 6 p.m. when the fire started.

The workers were taken to the hospital for minor burns.

“We had four workers from the gas company that presented to us with some minor burns they were conscious and alert, talking and they were all transported to the Brigham and Women’s Hospital to be treated and more than likely released,” said Boston EMS Deputy Supt. Ed Hassan.

Boston Firefighters at gas main fire in Roslindale (Image credit Boston Fire/Twitter)

Three triple-deckers were evacuated as a precaution.

The fire was still burning early Monday morning. Workers cannot shut off the gas because that would cut off heat to 8,200 homes in the bitter cold.

Gas main fire on Hyde Park Ave in Roslindale (WBZ-TV)

Workers tried to bring in heavy equipment to push sand on top of the burning gas leak to smother it, but officials were concerned about the gas getting into nearby homes.

“My biggest concern right now is the migration of gas underground because it’s a high pressure main,” said Boston Fire Commissioner Joseph Finn. “If we smother it too much without some vent holes it could migrate into some of these other households, that’s a big concern right now.”

The cause of the fire is unknown.