An 8-year-old boy and the horse he was riding were struck by lightning and killed in the Rancho Nuevo recreation park in San Cristobal de Las Casas in the southern Mexican state of Chiapas, authorities said.

The lightning bolt also injured two of the boy's female cousins, ages 8 and 16, Chiapas emergency-management officials said Thursday.

The three minors on a visit from Mexico City were horseback-riding together, but the injuries to the two girls were so slight they required no hospitalization.

The place where the lightning struck is an ecological park where locals rent out their horses to tourists.

The Chiapas emergency-management office said that there are currently heavy rains with strong electrical activity in this wooded area, whose caves are some of its main tourist attractions.

Ten people have now died during the Chiapas rainy season - two hit by lightning, four swept away in their cars by overflowing rivers, three children drowned in the Grijalva River and a girl buried under a mudslide in the municipality of Mapastepec.