A Calvert County sheriff’s deputy suffered serious injuries early Thursday after he was involved in a four-vehicle crash in southern Maryland.

The crash happened just after 6 a.m. along Route 4 near Cox Road in Huntingtown, officials said. A vehicle rear-ended the deputy’s unmarked vehicle, causing a chain reaction as he rear-ended another vehicle. He was on duty at the time, officials said.

Two others suffered minor injuries in the collision.

The deputy was taken to a shock trauma center with injuries not considered to be life-threatening. Roads in the area were closed during an investigation.