The parents of 43 missing students who disappeared in September 2014 are accusing the government of lying to them, planting evidence and not adequately investigating the case.

The parents' comments come a day after a group of international experts issued a report criticizing the investigation.

The report says suspects appear to have been tortured and key pieces of evidence related to the supposed burning of the students' bodies were not correctly investigated.

Parent Mario Cesar Gonzalez said Monday that prosecutors had lied and planted a bag of charred bone fragments. Tests have linked the fragments to only one of the students.

The government says a drug gang killed and burned the students. Parents reject that.

Human rights activist Mario Patron said the torture allegations endanger efforts to find the truth.