Mexican officials say gunmen killed four people in an attack on an ambulance in the border city of Ciudad Juarez.
Witnesses say a pick up truck carrying the gunmen rammed the ambulance Wednesday, forcing it to stop.
They say the suspects got out of the truck and opened fire, killing the ambulance driver, two kidney patients, and a fourth person.
No motive has been given for the attack, but Ciudad Juarez, which is across the border from El Paso,Texas has a history of drug-related killings.
Reuters news agency says more than 1,800 people have been killed in Ciudad Juarez 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.
About 30,000 people have been killed in Mexico's drug war since President Calderon took office in late 2006 and began cracking down on the cartels.
Some information for this report was provided by AP, AFP and Reuters.