Ann Davis, a spokeswoman for the TSA, released a statement last night saying, “We will work with the airport, which is responsible for access control security, to conduct a thorough investigation based on the facts and information provided by law enforcement.’’

He said he notified federal officials yesterday that Tisdale somehow managed to breach security at the Charlotte airport.

He added, “It’s a terrible tragedy, what happened to this young man, but if that was someone with a different motive . . . if that was a terrorist, that could have been a bomb that was planted, undetected. This is very serious.’’

“There is great concern that with all of our efforts for security and the almost invasive type of efforts that are occurring right now, that something like this could happen,’’ said Keating, who will be sworn in next month as the new congressman from the 10th Congressional District.

Keating said that it was unclear how the teenager was able to get onto the tarmac and climb into the wheel well undetected at a time of heightened security, but that the probability that he did so raised troubling questions about the potential for a terrorist attack.

“It appears more likely than not that Mr. Tisdale was able to breach airport security and hide in the wheel well of a commercial jet airliner without being detected by airport security,’’ Keating said during a press conference, calling it a major breach of airport security.

The conclusion that the teenager’s death was not believed to be a homicide, as initially thought, quickly shifted the focus of the investigation to the Charlotte airport and the Transportation Security Administration.

Fingerprints and a handprint were also discovered in the left wheel well of a Boeing 737 commercial airliner that left Charlotte Douglas International Airport at 7 p.m. Nov. 15 and landed at Logan about two hours later, Keating said. Investigators are still awaiting test results to confirm that the prints are Tisdale’s, but Keating said it appears likely that they are.

A shirt stained with what appeared to be grease used in airplanes and believed to be Delvonte Tisdale’s was recovered yesterday, along with sneakers, scattered along the flight path, Keating said. The items were found about a half-mile from where the 16-year-old’s body was discovered on Brierbrook Street on the night of Nov. 15, authorities said.

A month after the mangled body of a North Carolina teenager was found in a quiet Milton neighborhood, Norfolk District Attorney William R. Keating said yesterday that evidence indicates he stowed away in the wheel well of a plane and fell from the sky as the landing gear came down on the approach to Logan International Airport.

Tisdale’s parents could not be reached for comment last night. But, Norman Brown, a former neighbor of Delvonte Tisdale in Baltimore who said he was like an uncle to the teenager, reacted with disbelief to the announcement that the teenager fell from a plane.

“It seems pretty far-fetched to me,’’ said Brown, questioning how he could have made it across the tarmac and onto a plane with the increased scrutiny of the TSA. “He would have to go into the terminal, find out where the plane is, and he’d have to go to TSA to get to where that plane is. Then he would have to orient himself once he got on the field. That’s just too much for a child to do.

“That just doesn’t sound right at all. . . . I think there’s more to be investigated here.’’

Diane Turner, the mother of Delvonte Tisdale’s half-brother, Craig Tisdale, was also skeptical of the notion that Tisdale fell from a plane.

“Even though he wanted to go into the service, he was afraid of flying,’’ said Turner, who lives in Baltimore and considered Delvonte her stepson. “I just can’t see that happening. But then again, I don’t know. I’m not a scientist. Only God knows what happened to Delvonte.’’

Tisdale, a sophomore who was enrolled in the Air Force Junior ROTC program at his high school in Charlotte, NC., was last seen by a sibling some time after 1:30 a.m. on Nov. 15.

Keating would not identify the plane Tisdale was believed to have been on, but when asked if it was a US Airways flight, he acknowledged it had been “identified as such.’’

US Airways spokesman Andrew Christie said last night that he could neither confirm nor deny that Tisdale was on a company plane. He said the airline is cooperating with the investigation and declined further comment.

Keating said he spoke yesterday with Tisdale’s parents, but declined to disclose what was said.

Keating said it is unclear why Tisdale, who had relatives in Baltimore, would stow away on a Boston-bound plane. He said that Brierbrook Street is in the direct flight path used by aircraft heading to Logan and that a resident heard a crashing noise shortly before 9 p.m. Tisdale’s battered body was discovered about a half-hour later. Police initially suspected that he was slain, but found no evidence of foul play.

The pants Tisdale was wearing were also stained with what is believed to be grease used in airplanes, Keating said.

It was unclear whether Tisdale had survived the flight until he fell from the plane, said Keating. He added that a plastic card Tisdale was believed to be carrying shattered when it hit the ground, “consistent with being frozen’’ in flight.

Laura J. Brown, a spokeswoman for the Federal Aviation Administration, said that it is not uncommon worldwide for stowaways to hide in plane wheel wells, but that it is rare on planes originating in America.

The last person to stow away on a flight from a US airport was on April 14, 1972, when a frozen body was found in the left wheel well of a flight from San Diego to New York City.

In February of this year, a frozen body was found in the wheel well on a flight from John F. Kennedy International Airport in New York when it landed at Narita International Airport in Japan, but it was later discovered that he did not actually stow away on the plane in New York. In fact, his body had been undetected in the wheel well since he stowed away Dec. 12, 2009, during a flight from Lagos, Nigeria, to New York.

Between 1996 and November of this year, there have been 86 stowaways involving 76 flights, of which 68 were fatal and 18 people survived.

John R. Ellement and Jonathan Saltzman of the Globe staff contributed to this report. Andersen can be reached at tandersen@globe.com; Murphy at shmurphy@globe.com.

© Copyright 2010 Globe Newspaper Company.