STAMFORD, Conn. (AP) — Authorities say three people have been injured in an explosion at a Connecticut water treatment plant.

Stamford fire Lt. Kevin Connell tells the Stamford Advocate that the explosion occurred just before 11 p.m. Thursday at the Stamford Water Pollution Control Authority. It was described as a “dust explosion” and Connell says there was no fire.

Three employees were taken to Stamford Hospital with minor injuries.

The explosion damaged several roll-up garage doors and several windows.

The city’s Building Department arrived at the scene at 3 a.m. Friday to determine whether the plant suffered any structural damage.

The Fire Marshal’s office is investigating and the federal Occupational Safety and Health Administration has been notified.

The plant processes wastewater from Stamford and Darien.