Mexican officials say gunmen killed four people in an attack on an ambulance in the border city of Ciudad Juárez.
Witnesses say a pickup truck carrying the gunmen rammed the ambulance Wednesday and forced it to stop.
They say the gunmen got out of the truck and opened fire and killed the ambulance driver, two kidney patients, and a fourth person.
No motive has been given for the attack, but Ciudad Juárez, which is across the border from El Paso, Texas, has a history of drug-related killings.
More than 1,800 people have been killed in Ciudad Juárez this year compared to more than 3,000 murders in 2010.
The city has been on the front line of Mexican President Felipe Calderon’s war on drug cartels.