Maryland offensive lineman Jordan McNair showed signs of extreme exhaustion, had difficulty standing upright while running a set of 110-yard sprints and was found to have a body temperature of 106 degrees at a local hospital before he died of heatstroke suffered during a football workout, multiple sources told ESPN.

The 19-year-old from Randallstown, Maryland, collapsed during an outdoor Terrapins workout on May 29. He died two weeks later. No cause of death has been officially released, but ESPN has learned of an official heatstroke conclusion and new details about what happened to McNair based upon interviews with multiple sources in and close to the Terrapins program, as well as two witnesses to the workout.

An ESPN reporter on Thursday and Friday provided details about this story and other findings on the overall football culture and asked Maryland officials for interviews or to comment. University officials on Friday afternoon said, "The University of Maryland has placed members of our athletics staff on administrative leave pending the outcome of the external review." No further details were provided.

McNair's death, and whether university coaches and officials followed proper protocols after he became distressed, are being investigated by Dr. Rod Walters, a university-hired, former longtime collegiate athletic trainer. Walters' report is expected to be released Sept. 15. McNair's parents have hired the Baltimore law firm of Murphy, Falcon & Murphy to investigate as well.

The May 29 workout, which was organized and led by the Maryland strength and conditioning staff, began at 4:15 p.m. ET. McNair and other linemen were near the end of their sprint set when McNair started having obvious difficulties, according to multiple sources. McNair family attorney Billy Murphy told ESPN on Thursday that McNair had a seizure at about 5 p.m., following a sprint.

"Our reading of the medical records and the 911 call Maryland made to the EMT to come to the field reveal that 45 minutes into the practice, he had convulsions and a seizure on the field," Murphy said, "and the 911 call reflects emergency personnel noted McNair had experienced a seizure."

A 911 call recording obtained by ESPN shows that at 5:58 p.m., an unidentified male described McNair as "hyperventilating after exercising and unable to control his breath."

After evaluating McNair at the football facilities, EMT responders called in "male patient with a seizure," and McNair was transported to Washington Adventist Hospital, according to the 911 call. He later was moved to Cowley Shock Trauma Center in Baltimore, where he remained until he died June 13.

"Our preliminary investigation reveals there is an unexplained one-hour time period when nothing significant was done to avoid the complications of heatstroke," Murphy said. "Although there is some evidence they allegedly tried to cool him down, he should have been iced immediately. He presented at the hospital with a temperature of 106, which means he was not cooled down.

"We're very concerned about the unexplained one hour between the time of the seizure and hyperventilating that was observed by a coach, and what happened in that remaining hour before the EMT people were actually called. This points to an utter disregard of the health of this player, and we are extraordinarily concerned that the coaches did not react appropriately to his injury."

Murphy said a lawsuit is "likely" to be filed.

Maryland officials had earlier Friday declined to be interviewed and instead issued a statement: "At no point before or during the external review has a student-athlete, athletic trainer or coach reported a seizure occurring at 5 p.m.

"We will be able to speak in greater detail when the review is complete and shared with the public. Our consultant has work to do to finish this investigation. We will take appropriate action when we have the full details. Our thoughts remain with Jordan McNair's family, friends and teammates."

In a letter sent Friday to the parents of Terrapins players that was obtained by The Baltimore Sun, Maryland coach DJ Durkin acknowledged that ESPN's reporting "may prompt questions" about the program but said "our priority every day is the safety along with the academic, personal and athletic development of your sons." Durkin added that the program is cooperating fully with the investigation and said he's available to address any questions the parents had themselves.

Maryland athletic director Damon Evans has said previously that the team gathered for a scheduled, supervised workout around 4:15 p.m. at its outdoor practice fields. The strength and conditioning staff, led by Rick Court, supervised the workout. Certified athletic trainers were present. It was about 80 degrees when the workouts began, and after a warm-up, the players were told to run 10 110-yard sprints.

Evans has said that McNair completed the entire workout before falling ill. He said trainers noticed that McNair was having some trouble recovering and began "providing necessary care."

But multiple witnesses at the workout told ESPN that McNair had physical difficulty before the workout ended and needed two teammates to help him complete the 10th sprint.

"There's no way he finished on his own," one of the players at the workout told ESPN.

"There were multiple people that said, 'Wow, Jordan looks f---ed up, he doesn't look all right,'" the player said. "We knew he was really exhausted, but we didn't know he was in danger of his life. But that doesn't mean that a medical professional shouldn't know to put him in an ice tub."

Multiple sources said that after the 10th sprint finished, Wes Robinson, Maryland's longtime head football trainer, yelled, "Drag his ass across the field!"

A second player at the workout told ESPN: "Jordan was obviously not in control of his body. He was flopping all around. There were two trainers on either side of him bearing a lot of weight. They interlocked their legs with his in order to keep him standing."

Maryland officials have said McNair "was talking to our trainers throughout" and that after the completion of the workout, the trainers "began supporting an active recovery and providing care."

Multiple sources estimated that trainers walked McNair around for about 80 yards after he started showing distress.

"They tried to walk him for a while after he collapsed," the second player who spoke to ESPN said. "His head, he barely had control over it. His head was limp to the point where it was back. They were walking him across the field to get him up and moving, I guess. But then they basically took him over to position drills, which took a long time. I didn't see them bring him in, but it was a while."

The first player who spoke to ESPN said: "It was a good [distance] for a guy in his state to be walking, and it was away from the athletic training building, away from any resource that he probably needed at the time. Probably 100 percent the opposite way."

Maryland officials said trainers walked with McNair as part of their active recovery efforts before he was taken by a motorized cart to the athletic training room in the football team house for "further observation and continued treatment."

Maryland players are required to receive a medical clearance at the start of the practice season, and all players participating in the May 29 workout had previously received medical clearances from team physicians to participate in football activities, according to the university. That heatstroke might have been the cause of McNair's death was first raised by his family on a personal website. His parents, Tonya Wilson and Martin McNair, declined comment for this story.

According to the Mayo Clinic, heatstroke can occur when a body temperature rises to 104 degrees or higher. It requires emergency treatment and "the damage worsens the longer treatment is delayed, increasing risk of serious complications or death."

College football reporters Adam Rittenberg and Tom VanHaaren contributed to this report.