Five children were killed and nine people were injured in central Mexico when lightning bolts struck a metal cross on a hillside as people decorated the cross in preparation for a May 3 religious holiday, authorities reported on Monday.

The accident occurred late Sunday at a rural site near the town of Santa Maria del Rio, in the state of San Luis Potosi, about 180 miles north of Mexico City.

The children were part of a group cleaning and decorating the approximately 10-meter (yard) tall cross in preparation for the May 3 Catholic celebration of the Day of the Holy Cross.

Nine people suffered serious injuries during the lightning strike and are being treated for their injuries at the state's Central Hospital, the state government said in a press statement.

A group of between 25 and 30 people had gathered Sunday afternoon at the hilltop, known as El Original, which features a simple metal cross atop a concrete base.

However, it began to rain and witnesses told state police that two lightening bolts struck the area around the base of the cross.

The state government identified the dead as two 13-year-old boys, a 14-year-old, and two girls aged 10 and 12.

In Mexico, the Day of the Holy Cross has been adopted as a festival for construction workers, who frequently attach wooden crosses to the structures on which they are working.