Fifteen people were killed on Wednesday at a car-washing centre in the western Mexican town of Tepic, in the third such massacre in less than a week in the country.
According to the authorities of the state of Nayarit, where Tepic lies, a group of armed attackers arrived at the Gamboa car wash and opened fire on workers and customers. Workers and two street food vendors were among the dead, the authorities told DPA. Two people were injured in the attack.
According to unofficial reports, some of the car-wash workers came from a drug rehabilitation centre.
On Friday, armed attackers who were apparently looking for a rival killed 14 young people at a birthday party in a Ciudad Juarez home.
On Sunday, 13 people were killed in Tijuana in a drug rehabilitation centre, in an alleged vendetta over the confiscation of 134 tonnes of marijuana by the authorities a few days earlier.
Nayarit, on the Pacific Ocean, is a state in which such massacres are rare, unlike in northern Mexican states.
More than 28,300 people have been killed in Mexico in incidents linked to organised crime since Mexican President Felipe Calderon was inaugurated in December 2006.