Government investigators began sorting through the Dallas Cowboys' flattened practice facility Monday, trying to figure out why fierce winds sent the tentlike structure crashing down during a rookie workout session.

Twelve people were hurt, including Cowboys special teams coach Joe DeCamillis, who underwent surgery Monday to stabilize a fractured vertebrae in his neck. The most seriously injured was Rich Behm, the team's 33-year-old scouting assistant who was permanently paralyzed from the waist down after his spine was severed. Assistant athletic trainer Greg Gaither, 35, had surgery on his fractured right leg. Both DeCamillis and Gaither are expected to get out of the hospital this week.

Inspectors were at the collapse site Monday, said Elizabeth Todd, a spokeswoman for the U.S. Occupational Safety and Health Administration. OSHA, which investigates workplace accidents, has six months to make a report, she said.

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Records obtained by The Associated Press show the city of Irving granted the Cowboys' request to replace the fabric roof last year, five years after the structure was built. The team listed itself as the contractor for the roof replacement, but Cowboys spokesman Rich Dalrymple said the team would not comment about the work.

The records do not show the Cowboys sought an inspection of the facility after replacing the roof, although city code requires it, according to Gary Miller, Irving's director of planning and inspections.

"In a perfect world, there's some report from an installation company or an engineer in there, but we don't have it," Miller said.

The company that built the facility — Summit Structures LLC of Allentown, Pa. — issued a statement that said proper engineering was used during the original construction and the installation of the new roof. Summit president Nathan Stobbe said he was in Irving on Monday, working with team and local officials to "fully assess this severe weather event." The company said it has few answers so far about precisely what happened.

About 70 people, including 27 players at a rookie minicamp, were inside when the storm hit. Winds were clocked at 64 mph, 1 mph shy of the threshold for a weak tornado. A "microburst" may have pushed the wind beyond 70 mph at the top of the structure, National Weather Service officials said

Behm, DeCamillis and Gaither were standing on the field when the $4 million structure gave way, sending framework, lights and other debris crashing to the ground.

None of the players were hurt. Coaches, support staff and media were also in the no-frills building, essentially a 100-yard football field with a few more yards of clearance all the way around. The roof was 80 feet high.

Media were restricted from the Cowboys headquarters for at least a week because of ongoing work that is scheduled to take place in the aftermath of the accident.

Summit lists on its Web site several other facilities it built, including one at Texas A&M and one for the New England Patriots. The company also built the Windstar Casino just across the Texas-Oklahoma border.

James Stacey, Patriots' executive director of media relations, said in an e-mail the Patriots were "reviewing all aspects of the facility."

The A&M facility is a $35.6 million project that includes both a football practice facility and an indoor track. A&M athletic director Bill Byrne said the school has had no problems with the project, completed late last year, but will re-evaluate its policy on bad weather practices considering the collapse in Irving.

"Our facility was put to the test this past fall when Hurricane Ike hit the Texas gulf coast," he said in a statement. "Our buildings withstood the high winds and our football team was not in the facility at that time."

At the University of New Mexico, which also has a Summit-built football practice facility, associate athletic director Scott Dotson said the collapse hasn't generated significant concerns there.

He said the school's facility "has been tested with some strong winds and held up."

A Pennsylvania court ruled in 2006 that Summit was negligent in the design and construction of a membrane-covered building that collapsed in 2003 after a major snowstorm in Philadelphia. The building was constructed for the Philadelphia Regional Port Authority.

City of Irving construction records list Oklahoma-based Manhattan Construction Group as the contractor for the Cowboys' facility and Summit as the structural engineer. Manhattan is the general contractor for the new Cowboys stadium that will open next season in Arlington.

Bob Bowen, Manhattan's executive vice president, said his company helped protect the outdoor practice field from damage during construction but all the planning and other work was done by Summit.

In a 2003 letter to then-Irving Fire Chief Paul White, Cowboys director of football operations Bruce Mays described the planned facility as "a semi-permanent structure supported by lightweight steel trusses and clad with a fire resistant polymer fabric."

Mays said preliminary discussions between the team and the city had concluded the building was "a unique type of structure and there could be a variety of interpretations as to what standards should be applied in evaluating the structure to comply with building and fire codes."