A gunman has opened fire in a manufacturing plant in the US state of Maryland, killing multiple people, police say.

According to Sky News partner NBC Washington, officers were called to the unit in the town of Smithsburg around 2.30pm (7.30pm GMT) on Thursday.

The Washington County Sheriff’s Office said there were “multiple fatalities,” including the state trooper who tried to chase down the the gunman.

The suspect was shot, injured and taken to hospital following a “confrontation” with a Maryland State Police trooper, the sheriff’s office said.

Maryland governor Larry Hogan said he believed there were at least three people injured fatally.

Congressman David Trone, whose constituency includes the town, said on Twitter he was monitoring a “mass shooting” in Smithsburg and urged residents to stay away.

Smithsburg, a community of nearly 3,000 people, is located about 75 miles northwest of Baltimore not far from the Maryland border with Pennsylvania.

The shooting comes less than two weeks after 21 people were killed when high-school dropout Salvador Ramos opened fire at an elementary school in the small community of Ulvade, Texas.