ATLANTA – The U.S. Department of Justice said Thursday that it had opened a formal review of the death of a 17-year-old boy found in a rolled-up wrestling mat at his Georgia high school in January.

The death of the student, Kendrick L. Johnson, has been the subject of questions since his body was found in the upright blue mat at Lowndes High School in Valdosta, Ga., on Jan. 11, a day after his mother reported him missing after a basketball game.

Although the state and local authorities determined that Johnson’s death was an accidental one caused by positional asphyxia, his parents, Kenneth and Jacquelyn Johnson, disagreed and called for a renewed inquiry.

Their lawyer, Benjamin L. Crump, said in a telephone interview, “It defies all logic, the laws of physics and common sense that a 17-year-old, an above-average athlete, would climb into a wrestling mat, get stuck trying to reach for a shoe and suffocate.”

The family commissioned a private autopsy that said “unexplained, apparent nonaccidental blunt force trauma” killed him.

Crump, who has also represented the family of Trayvon Martin, the unarmed youth fatally shot in Florida last year, said the Johnsons were pleased that the Justice Department had chosen to intervene.

“They are relieved today, but they know it’s a journey,” Crump said. “We are optimistic that we are going to get to the truth.”

In deciding that further investigation was warranted, Michael J. Moore, the U.S. attorney for the Middle District of Georgia, said, “There are several questions that must be answered or confirmed,” including whether criminal misconduct was involved.

“I do this with an open mind, neither accepting nor rejecting the opinions of anyone who has previously investigated the circumstances of his death,” Moore said.

The Lowndes County sheriff’s office, which was ordered Wednesday to provide the records of its investigation to Johnson’s parents, declined to comment beyond an interview the sheriff, Chris Prine, gave to the Valdosta Daily Times this week.

The sheriff said he would welcome the federal review.

“Our investigators have remained objective and explored all avenues that were presented, including rumors,” Prine told the newspaper. “Each time a bit of information was learned, investigators made every possible effort to examine the information and interview the persons named.”

Moore said the FBI was “cooperating” with his review, which could ultimately include an inquiry into whether Johnson’s civil rights were criminally violated.

The prosecutor did not say how long his review might take, and a judge is expected to rule next week on a bid by the youth’s parents for a coroner’s inquest.

Family members said they would continue to press for the truth.

“We always believed it wasn’t an accident, and we still believe it wasn’t an accident and we always will believe it wasn’t an accident,” Kenneth Johnson told AP on Thursday.