Fifty-four people were injured early Sunday when a bus overturned on an intercity road in Iran's central Semnan province, according to the official news agency IRNA.

The incident took place on the route from Sorkheh County to the provincial capital, Semnan, at 4:45 a.m. local time (0115 GMT), said Karen Yahyaei, spokesperson for Semnan University of Medical Sciences and Health Services.

Yahyaei added that 10 ambulances and one ambulance bus swiftly transported the injured to a hospital in Semnan.

Semnan's Traffic Police Chief, Mousa Bozorgi, stated that the bus had veered off the road due to the driver's drowsiness, according to the semi-official Mehr news agency.

An investigation is currently underway to determine the exact cause of the accident.