Hannaford Supermarket in Bangor was forced to evacuate customers Thursday, after a frozen sprinkler system leaked.
It happened just before 5 pm.
Initially, some employees thought there was a gas leak.
Responders say the building’s iron pipes are coated with an oily residue and when they burst, a dark colored liquid comes out.
Firefighters say there was minimal damage.
They helped sweep the water out and cleared the scene within an hour.
The supermarket is back open and operating as usual.