(CNN) -- At least five of the bodies found this week in a shallow grave near Mexico City are those of teens who were kidnapped from a bar three months ago, Mexico's attorney general said Friday.
The announcement appears to shed light on a crime that jolted the capital city: The kidnapping of 12 youths from an after-hours club during daylight on the morning of May 26.
Authorities on Thursday said they found a clandestine mass grave east of Mexico City. On Friday, the federal attorney general said the grave -- a shallow grave covered by concrete at an eco park in a state neighboring Mexico City -- contained 13 bodies.
Five of them were those of youths who'd been taken from the Mexico City club, the attorney general said.
Earlier, authorities said the grave was at a ranch. The site is in the town of Tlalmanalco, in the state of Mexico, about 30 miles east of Mexico City, the state-run Notimex news agency reported.
Authorities haven't said what led them to the grave.
The May 26 incident at the after-hours bar shocked residents of Mexico City, who for the most part have been spared from the violence seen in other areas.
The owner of the bar, a co-owner and two bar employees have been arrested in the case.
CNNMexico's Veronica Diaz and Juan Pablo Mayorga contributed to this report.