Mexican investigators questioned eight people in connection with the rape of six Spanish tourists in Acapulco, as officials scrambled to contain the potential damage on tourism.
Around five gunmen wearing masks burst into a beach bungalow where 14 tourists were staying late Monday, tying up seven Spanish men and raping the six Spanish women while sparing a Mexican woman.
The assault has further tarnished the reputation of Acapulco, a once glitzy haunt of Hollywood stars such as Frank Sinatra and Elizabeth Taylor that has been beset by drug violence in recent years.
Police in quad bikes and boats combed the beach for suspects while soldiers set up security posts along the road leading to the district of Barra Vieja, where the rapes took place.
Authorities stressed that the eight people who were questioned had not been detained.
"They are people whom we are questioning with intensity to find out what they know about this," Marcos Juarez, director of the Guerrero state investigative police, told reporters.
"They are people who were closest to these questions. They are not detainees," he added.
Governor Angel Aguirre Rivero said he would hold a news conference on Thursday to give the first results of the investigation.
"This will not remain unpunished. I share your pain and indignation," he said.
Aguirre Rivero met Wednesday with Interior Minister Miguel Angel Osorio Chong to discuss the violence in the state, which has prompted farmers in rural mountains to set up armed vigilante squads.
Mexico has sought to clean up its image as a violent country in order to convince tourists to keep coming despite more than 70,000 drug-related deaths since 2006.
Acapulco has seen its share of drug violence, with gangs dumping the bodies and heads of rivals in the street. It still attracts nine million visitors a year, though only one third are foreigners.
Seventeen gangs are believed to operate in Acapulco, and some have links to two drug cartels, the Zetas and their rivals, the Knights Templar.
"We will have to do a very big campaign so that an event like this one does not affect and hurt visitors in an important way," the governor said. "This is why we hope to detain the culprits soon and punish them."
The state attorney general, Martha Elva Garzon, said the suspects' motive was to steal "and amuse themselves," and that they spared the lone Mexican woman because of they determined "she passed the test by being Mexican."
Meanwhile, Acapulco Mayor Luis Walton Aburto urged President Enrique Pena Nieto to deploy more federal security following the sexual assault.
"Today we have not seen the support of the president, and we are demanding that he return to see Acapulco," Walton Aburto said. "Acapulco has a lot of needs."
The mayor was forced to apologize after causing outrage by saying that the crime was something that "happens everywhere in the world."
The Acapulco hotel industry fears that foreign nations will maintain their travel alerts on Acapulco a while longer.
The president of the Acapulco Hotel and Tourism Industry Association, Mary Bertha Medina, urged tourists to stay in hotels rather than beach houses, which she said lack security.
"It is very hard for a commando of this size to enter into a hotel," she said. "It is difficult and it has never happened."