The official, who has knowledge of the case, said police are pursuing strong leads, CNN reported.
Military checkpoints have been set up and investigators have cordoned the bungalow in Acapulco as they sift through evidence.
Attorney General Martha Garzon said the men who attacked the six women and tied up seven men do not appear to be members of an organized gang.
A Mexican woman with the group was not sexually assaulted.
Garzon said during a radio interview five armed men, wearing hoods, entered the villa where the tourists were staying and attacked them, El Universal reported.
Besides the assault, the men stole laptop computers, cellphones, credit cards and other items.
The prosecutor said the search has expanded but "significant progress" has been made, adding he expected "positive results" soon.
Asked why the Mexican woman wasn't raped, Garzon said she identified herself as Mexican, asked not to be raped and "hence was not touched," he said.
He said municipal, state and federal offices were involved in the search for the assailants. The Spanish victims have been in contact with their country's diplomatic officials in Mexico.