The attorney general's office says the remains of 129 bodies have been recovered from the graves.
None of the remains have been linked to the students who vanished in Iguala.
The information was released after a freedom of information request by the Associated Press.
The majority of the bodies are male, but the remains of some 20 women were also found.
The unmarked graves were discovered during the huge investigation into the disappearance of the 43 students.
The number of mass graves found from October to May could be higher because the information given to AP only covers instances in which specialists became involved.
The students, from a teachers' college in Guerrero, had travelled to Iguala and, as part of a protest, commandeered a number of buses.
The government says the 43 were intercepted by police and handed to members of a drugs gang who killed them and incinerated their bodies.
Gang members confessed to killing the students and burning their bodies after they were mistakenly told they belonged to a rival gang.
The badly burnt remains of one student have been found at a rubbish dump, but many families of the remaining 42 refuse to believe the students are dead.
Correspondents say the case has highlighted the huge number of people who have gone missing in Mexican states where drug violence is widespread.

And Team GB's youngest star, bronze-winning gymnast Amy Tinkler, who last week was wowing global sports fans but tomorrow collects her GCSE results, was given the welcome home of a sporting hero.
There were several false starts as friends, coaches and fans waited at her gymnastics club to welcome her back after her Rio exploits.
Twice the motivational music was started on the loud speaker as twice someone who was not the 16-year-old came in the door.
But on the third go (you might say in the bronze medal place), the real deal arrived and the welcome was emotional to say the least.
She was quickly at the centre of a huddle of young girls for whom she represents the reality that dreams can come true.
And then there were cuddles from her coaches, who have spent hours in the South Durham Gymnastics Club helping Amy hone her skills for the Olympic Games.
Finally there was the media scrum. Local newspapers who had reported on Amy's various championship successes for years, radio stations and TV journalists all waited for their chance to talk to County Durham's newest Olympian.
Amy said: "To see everyone back here is overwhelming.
"It's incredible, it's starting to sink in but it still seems crazy that it actually has happened.
"(The medal) has been very close to me all the time. I was sat on the plane and the whole way back I had it on, it's just so special to me."
For someone who the day before had flown the best part of 5,800 miles (9,300km), she looked remarkably refreshed.
"I didn't get much sleep on the plane to be honest," she said.
"I was sat near the hockey girls (the gold-winning women's hockey team were the ones filmed singing God Save the Queen), then we had like a six-hour drive to get home, but once I finally got home yesterday evening I slept really well.
"I've got a busy week with interviews and media, next week I'll have time chilling with family and friends, then the week after that I'll get back into training."
And on top of all that, tomorrow she gets her GCSE results, not that she's worried.
"It is what it is, I have to get them," she said.
The welcome-home party started as soon as she returned to her housing estate on the edge of Bishop Auckland, with neighbours ready to greet her.
Young fans got autographs, older ones told Amy how proud they were of her.
But it was at the gymnastics club, a large pink sports hall with a Â£30,000 floor and various beams, balance bars, trampolines and foam-filled pits, that she was really able to celebrate her success.
"She started here when she was two-years-old" said Nicola Preston, her coach for the past 14 years.
"She is one of the family, we are all just so proud of her, we are pleased to have her home, we've really missed."
Barely 20 minutes after Amy's arrival, the next generation of gymnasts were back to training on the various pieces of equipment.
One young girl said: "Amy is an inspiration, she's shown us what can be done. She worked really hard, she deserves what she's got."
Sixty mass graves have been uncovered in the southern Mexican state of Guerrero during a search for 43 student teachers abducted last September, official documents have revealed.
[NEXT_CONCEPT]
She went to Rio a hopeful but came back an Olympic medal holder.