A group of gunmen attacked an ambulance in this northern Mexican border city, killing two paramedics and two male patients and wounding a female patient, authorities said.

The victims were traveling from the city of Nuevo Casas Grandes to Ciudad Juarez - a distance of 277 kilometers (170 miles) - when an SUV collided with the ambulance and forced it to stop, Juarez municipal police spokespersons told Efe.

At the time of Wednesday’s attack, the patients were being transferred from an IMSS insurance and social services agency hospital to a clinic in Ciudad Juarez for treatment for kidney failure.