Another woman, also in the bungalow, was not attacked during the incident early Monday morning near the beach resort city, known as a top spring break destination for vacationing tourists.
The victims — Spanish nationals in their 20s on vacation — are now under the protection of Mexican authorities. Spanish officials have been notified.
Acapulco Mayor Luis Walton condemned the attack during a Tuesday news conference and vowed to apprehend those responsible.
“It’s a very delicate situation,” he said. “We are going to have the full weight of the law against those responsible.”
He called the attack regrettable, apologized for it and said it would probably affect the image of Acapulco, which derives much of its revenue from tourism.
State prosecutor Martha Elba Garzon said her office would not reveal the names of the victims or anything related to the investigation, but she vowed to uphold the “responsibility to provide security to tourists and our people.”
Acapulco, in the state of Guerrero on Mexico’s Pacific coast, is generally thought of as a relatively safe city despite rampant violence in the surrounding region.
But it has been plagued by fiscal troubles in the wake of the global financial crisis and an uptick in violent crime. After a series of gruesome murders in Guerrero in the past few years, American and British authorities issued travel warnings.
In recent years, the region’s drug wars are thought to have impacted the city’s tourism sector as rival cartels vie for control of drug routes from South America.
Hotel occupancy rates across the Acapulco region now hover around 46%, according to the Secretariat of Tourism Development.
Image problem notwithstanding, Mexico has remained a top tourist destination for decades. It welcomed 20 million Americans in 2010, the latest year for which federal is data available.
But the U.S. State Department said resort city bars, including those in Acapulco, can be “havens for drug dealers and petty criminals.”
The agency said “resort areas and tourist destinations in Mexico generally do not see the levels of drug-related violence and crime reported in the border region and in areas along major trafficking routes.”
Spain’s Foreign Ministry advises travelers that “while foreign tourists rarely are victims of kidnapping or extortion, they can be victims of assaults and robberies.”
It said the mountainous state of Guerrero “should especially be avoided,” or travelers should proceed with “extreme caution.”
“In Acapulco, organized crime has carried out violent incidents, although until now they have not affected foreign tourists or the places they frequent,” the agency said.
An estimated 107,000 Spaniards live in Mexico. They reside mostly in the capital.
CNN’s Ariel Crespo in Mexico City, Al Goodman in Madrid, and Nick Valencia and Catherine Shoichet in Atlanta contributed to this report. Salomon Kauffman contributed to this report from Acapulco.