BALTIMORE — Members of Congress pressed for more information about how a giant surveillance balloon broke free of its moorings at Aberdeen Proving Ground, as troops resorted to shotgun blasts Thursday to deflate the grounded aircraft.

The unmanned aerostat escaped from the Army installation about noon Wednesday and drifted 160 miles north before returning to earth near Moreland Township, Pa., some four hours later.

The 243-foot JLENS balloon, one of two that have hovered over the Baltimore area this year, traveled at an average speed of 40 mph while trailing 6,700 feet of cable. Authorities scrambled two F-16 fighter jets from a base near Atlantic City, N.J., and warned onlookers away.

No injuries were reported, but the balloon snapped power lines in Pennsylvania, cutting power to thousands.

Rep. C.A. “Dutch” Ruppersberger, whose district includes Aberdeen Proving Ground — and who in 2013 promoted the Pentagon’s plan to bring the JLENS over-the-horizon radar system to Maryland for a three-year exercise — said Thursday he had asked the military for a full report on the incident.

“I want to find out what happened, who’s accountable and how we’re going to fix it,” he said.

Officials had few answers Thursday. The Army pledged a thorough investigation; a second balloon was hauled down and grounded Wednesday.

Sen. Barbara Mikulski, D-Md., asked commanders to review whether the exercise should continue.

“The Army must investigate the danger this incident posed to communities and determine what action needs to be taken to ensure this never happens again,” Mikulski wrote in a letter to Army Secretary John McHugh. “Determine whether operational testing for JLENS should continue.”

Capt. Matt Villa, an Army planning officer who was on the scene Thursday, said the balloon’s tail had come off and crews had to cut parts of the tether that had tangled in power lines.