Four people were seriously injured when the driver of an 18-wheeler swerved in an attempt to miss a cow on Highway 34 in Kaufman County.

The cow was killed in the accident.

The accident happened at about 4 a.m. Friday and led to a shut down of the highway between Interstate 20 and FM 2728. Officials say drivers should avoid the area as they work to investigate and clear the scene.

RELATED: Check traffic conditions

The driver of the 18-wheeler was headed southbound when a cow was spotted on the highway, said DPS Trooper Kyle Bradford. The truck struck a tree and overturned when the driver swerved in an attempt to avoid the animal.

While injuries were reported, the exact conditions of the four people who were inside the 18-wheeler aren't known.