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The parents of a Georgia teenager found dead inside a rolled-up gym mat two years ago filed a lawsuit accusing classmates of killing him at school before criminal investigators and school officials covered up the deed.

The wrongful death lawsuit by the family of 17-year-old Kendrick Johnson of Valdosta names 38 defendants, including three Lowndes High School classmates the lawsuit accuses of attacking Johnson on Jan. 10, 2013. The suit was filed in DeKalb County Superior Court on Monday, just after the second anniversary of the teenager's death.

Lowndes County sheriff's investigators concluded long ago that Johnson died in a freak accident, saying he became stuck upside down while trying to retrieve a gym shoe that fell into the upright mat. His parents, Kenneth and Jacquelyn Johnson, insist their son was slain. The lawsuit names specific students and one parent blamed for the teenager's death by his family, who are seeking $100 million in damages. However, no one has been charged with a crime in the case.

The lawsuit also says Johnson's slaying was covered up in a conspiracy involving the local school superintendent, the Valdosta police chief, the director of the Georgia Bureau of Investigation, five GBI agents, 17 sheriff's investigators and deputies, the state medical examiner who conducted the autopsy and others.

"Defendants from the various law enforcement agencies deliberately and maliciously mishandled the subject investigation in such a way that anyone who might ever be charged with (Johnson's) death would never be convicted," the lawsuit says.

James Elliott, who represents the sheriff's department as the attorney for Lowndes County, said the accusations "are unfounded and lack any basis in law or in fact."

The lawsuit filed by attorney Chevene King says the attack on Johnson was spearheaded by two brothers "seeking revenge" after one of them had been in a fight with Johnson. It also says the boys acted on a "parental command" from their father to assault Johnson.

"It's a frivolous lawsuit," said Brice Ladson, an attorney for the brothers and their father. "Mr. King and his clients, the Johnsons, know the allegations against my clients are completely baseless."

Sheriff's investigators say Johnson had been in a fight with one of the brothers about a year before his death. Sheriff's Lt. Stryde Jones said Thursday evidence showed neither brother was in the school gym when Johnson was recorded by a surveillance camera entering the building shortly after 1 p.m. One brother was in another part of the school, Jones said, while the other was traveling out of town with a sports team.

"We've chased a lot of rumor in this case," Jones said. "But we've been presented no evidence to the contrary at this point."

Lawyers for the Johnson family, King and Benjamin Crump, did not immediately return phone and email messages Thursday.

Federal authorities launched their own investigation in Johnson's death on Oct. 31, 2013. No findings have been released more than a year later.

"While our investigation has proven more complicated and taken longer than I had originally anticipated, we remain committed to following the facts wherever they may lead," U.S. Attorney Michael Moore of Georgia's Middle District said in a statement last week.