"We do now have six people arrested, who have confessed to everything," including a 16-year-old, Attorney General Jesus Murillo Karam told a press conference.
Gunmen wearing masks burst into a beach bungalow where 14 tourists were staying on February 4. They tied up seven Spanish men and raped the six Spanish women, while sparing a Mexican woman.
Mexico has sought to clean up its image as a violent country in order to convince tourists to keep coming, despite having seen 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 a third are foreigners.
The recent assaults further tarnished the reputation of the Pacific port city, a once glitzy haunt of Hollywood stars such as Frank Sinatra and Elizabeth Taylor that has been beset by violence in recent years.
It also is a popular draw for thousands of US university students on spring break vacations.
Seventeen gangs are believed to operate in Acapulco, and some have links to two rival drug cartels, known as the Zetas and the Knights Templar.
Meanwhile, President Enrique Pena Nieto said the government would place greater emphasis on guaranteeing the security of visitors from within Mexico as well as those from overseas.
"We have to offer tourists a climate of complete security," he said in the northwestern resort city of Bahia de Banderas while discussing the
government's plans to encourage the vital tourism sector.
"We will continue working to improve public security conditions."