Mexico City, July 4 : At least eight people were killed and another 30 injured on Monday when a passenger bus traveling from the United States overturned on the Zacatecas-Saltillo highway in central Mexico.

The accident occurred at around 6:30 a.m. local time (1230 GMT) in Rocamontes District of the city of Concepcion de Oro, Zacatecas, the National Civil Protection Coordination said on Twitter.

According to local media, the bus was carrying Mexican citizens residing in the United States to their hometowns in Zacatecas and Aguascalientes to spend summer vacation.

Preliminary reports said the accident may have been the result of speeding on slick asphalt following rain, causing the bus driver to lose control of the vehicle.

After the accident, paramedics treated the injured and transferred the most serious to the hospital.