CANCUN, Mexico — Two masked men armed opened fire in a bar on the outskirts of the Mexican tourist resort of Cancun on Thursday, killing six people and wounding five, the office of the state’s attorney general said.

Public Safety Secretary Jesus Aiza says most of the victims belonged to a taxi drivers union.

Aiza says the assailants arrived at “The Mermaid” bar in a poor area far from Cancun’s hotel zone in two cars Thursday afternoon. He says two gunmen using automatic rifles went inside and began shooting.

Aiza says soldiers are guarding the hospital where the wounded are being treated.

Police are still trying to determine a motive for the attack.

The killings came as tens of thousands of US college student flooded into the Mexican city where officials have stepped up patrols of marines and soldiers in tourist areas.

City officials said they expected up to 43,000 spring breakers, a significant increase over the roughly 25,000 that visited in 2012.

Cancun, a major tourist destination on Mexico’s Caribbean coast, has largely escaped the drug-related violence that has racked Acapulco, a faded tourist hot spot on the Pacific coast.

Last month, six Spanish women were raped by hooded gunmen who forced their way into the Acapulco beach house the women had rented.

The hours-long assault was carried out by a gang of 15 masked gunmen who burst into the beachfront home and tied up the six men inside with phone cords and the straps from bathing suits and then raped the women. A seventh Mexican woman was unharmed.

Mexican President Enrique Pena Nieto has vowed to reduce the violence that soared after his predecessor, Felipe Calderon, launched an assault on drug cartels.

More than 70,000 people have been killed in drug-related violence in Mexico since 2007.

With AP and Reuters.