MEXICO CITY, Dec. 27 (Xinhua) -- A passenger bus plunged some four meters off an overpass in north-central Mexico on Thursday, killing seven people and injuring at least 14.

The accident occurred at 7:50 a.m. local time (1350 GMT) along Highway 57, near the city of Santa Maria del Rio in the south of San Luis Potosi state, the local prosecutor's office said via Twitter.

Five of the fatal victims were killed at the site of the crash and two died while receiving treatment at a hospital. Two minors were among them.

The injured were taken to area hospitals in the state capital San Luis Potosi, which is located some 55 km north of the accident site.

The bus was heading from the border city of Nuevo Laredo, in northeast Tamaulipas state, to several destinations in central Guanajuato and Michoacan states.

Images of the aftermath published by local media, including El Sol de San Luis Potosi, showed a white bus lying on its right side, roof partially collapsing, as rescue workers attended victims lying on the ground.

Authorities have yet to determine what caused the accident.