CAPE CANAVERAL, Fla. – In what could be a breakthrough in the Columbia accident inquiry, foam shot at a fiberglass mock-up of a space shuttle wing knocked loose a seal — the same type of piece that investigators believe was damaged during liftoff.

“We’re not drawing any conclusions,” said Air Force Lt. Col. Woody Woodyard, a spokesman for the Columbia Accident Investigation Board. “We’ve got to analyze the data and evaluate all the data before we can draw any conclusions.”

But he described Thursday’s result as “significant.”

The Columbia Accident Investigation Board suspects a seal along the leading edge of Columbia’s left wing was damaged when struck by a chunk of foam insulation that broke off the fuel tank during launch.

In the first and only shot of the day at Southwest Research Institute in San Antonio, a 1.67-pound piece of real space shuttle foam was fired at the fiberglass leading edge at 533 mph. The foam blasted through the 33-foot barrel of a nitrogen-pressurized gun toward pretend panel No. 6 on the leading edge, tilted at a 20-degree angle.

Upon impact, the adjacent seal lifted and pulled toward panel No. 7, leaving an opening about 22 inches long, Woodyard said. The width of the gap ranged from the thickness of a dime to more than a quarter-inch.

All the parts in the abbreviated leading edge were fiberglass and came from the never-launched shuttle prototype Enterprise, which is housed at the Smithsonian Institution in Washington, Woodyard said. In highly anticipated testing in June, researchers plan to shoot foam at real carbon-composite wing pieces that actually flew in space.

Fiberglass is about 2 1/2 times more resilient than the carbon composite material that makes up real wing panels and seals, Woodyard said. That would suggest that a real panel or seal would have been even more damaged by a foam strike.

Thursday’s result was within impact predictions, Woodyard said. Earlier this month, researchers in San Antonio fired foam at the silica-glass thermal tiles that cover much of the space shuttles, but little if any damage resulted — also no surprise.

On Wednesday, the Columbia Accident Investigation Board said a mystery object that floated away from the shuttle on Flight Day 2 back in January almost certainly was half of a leading-edge seal. Such a long, narrow slit would be enough to let in the scorching gases of atmospheric re-entry, and that hole likely would have grown as the shuttle continued its descent, enough to cause its breakup over Texas on Feb. 1.

All seven astronauts were killed, just minutes short of their Florida homecoming.

The board’s chairman, retired Navy Adm. Harold Gehman Jr., has been reluctant to pin the blame on the foam strike, saying he lacks hard proof. He also has stressed that the impact tests in San Antonio will show whether foam could damage a shuttle wing — not whether it actually did. But others on the 13-member panel are convinced the foam led to the shuttle’s destruction.

A final report by the board is expected by the end of July.