News emerged Sunday of the Friday attack at the park east of Mexico City, where about 85 people were camping, the El Sol de Mexico newspaper reported.
Police said 12 heavily armed men and a woman held the camp hostage for several hours after sunset, raped the girls, and stole valuables and two vehicles.
Officials said they had two strong leads in identifying some of the suspects, but didn't elaborate.
Investigators were creating sketches of the suspects based on campers' accounts of the attack, the newspaper said.
The area is known to be a hub for drug dealers and gang activity, the report said.