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Authorities have "firm signs to find those responsible" for the rape of six Spanish tourists on the outskirts of the Pacific resort city of Acapulco, the attorney general of the southern Mexican state of Guerrero said Tuesday.

Though unwilling to go into detail, Martha Elva Garzon told Radio Formula investigators have made "important advances" toward solving the case.

The sexual assaults occurred around 3:00 a.m. Monday in Playa Bonfil, located in the eastern section of Acapulco, one of Mexico's most popular tourist destinations.

The victims and several male companions were outside their bungalow when five masked assailants armed with handguns accosted the group.

After gagging the men, the attackers forced the group inside the bungalow and assaulted the six Spanish women, though they spared a Mexican woman who was with them, the state attorney general said.

The ordeal lasted for about three hours and the assailants took PCs, cell phones, credit cards and other valuables when they left, Garzon said.

Acapulco has been plagued by drug-related violence in recent years.

The Guerrero state government launched a security operation in 2011 with the support of the federal government to step up security in areas frequented by foreign and domestic tourists.

"Operation Safe Guerrero" was launched on Oct. 6, 2011, in an effort to reduce the soaring crime rate in the state. EFE