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WASHINGTON — An unmanned Army surveillance blimp broke free of its mooring at a Maryland proving ground Wednesday and drifted more than 120 miles north into Pennsylvania, dragging a long tether that knocked out power to thousands, officials said.

The 243-foot-long, helium-filled aerostat broke free from Aberdeen Proving Ground at around 12:20 p.m., and a pair of F-16 fighter jets were scrambled to track it as it drifted north, before the blimp came down more than 3 hours later, North American Aerospace Defense Command said.

Sylvia Hock and her 9-year-old son, Aidan, were getting out of their car at their Millville home when they spotted the blimp overhead.

An unmanned Army surveillance blimp which broke loose from its ground tether in Maryland floats through the air about 1,000 feet about the ground while dragging a several thousand foot tether line just south of Millville, Pa., Wednesday, Oct. 28, 2015. Jimmy May / Bloomsburg Press Enterprise via AP

"We thought it was going to land," Hock told NBC News. "We thought it was going to pop, it got so low. We called 911, who said they were tracking it."

She said the blimp was dragging a cable, and "as it went it tore into lines and ripped poles out of ground."

The Joint Land Attack Cruise Missile Defense Elevated Netted Sensor System (JLENS) surveillance aerostat landed at around 4 p.m. in a wooded area near Moreland Township, Pennsylvania, NORAD said.

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There were no injuries reported. NORAD said a military recovery team was on the way to the area. Moreland Township is about 20 miles east of Williamsport, and about 120 miles northwest of the proving ground. At one point the blimp climbed to 16,000 feet, NORAD said.

The blimp had a tether of approximately 6,700 feet — more than a mile — attached when it broke free, Aberdeen Proving Ground said.

The dragging cable knocked out power to around 30,000 people in Pennsylvania, Gov. Tom Wolf's office said in a statement. By Wednesday night power was restored to most customers, with 311 without electricity as of 11 p.m., power company PPL Electric said.

If the #blimp has damaged your property, submit a claim with the Army Claims Services at 301-677-9076. — Senator Pat Toomey (@SenToomey) October 28, 2015

Power company PPL Electric Utilities said it was assessing damage caused by the cable, which occurred mainly in Columbia and Schuylkill counties, which are south of where the blimp came down.

The F-16 fighter jets, scrambled out of Atlantic City, New Jersey, followed the blimp but there was no thought of shooting the aerostat down, NORAD officials said.

The tail section detached first, and was found about a quarter-mile from where the rest of the blimp landed, officials said.

RELATED: Facts About The Wayward Blimp

Ground controllers at Aberdeen Proving Ground do have the ability to deflate the helium-filled blimp but did not so so, NORAD said. It is unclear if an auto-deflate system activated and caused the blimp to descend, officials said.

Jason Jarinko, at teacher at Central Columbia High School in Bloomsburg, told The Associated Press that a student gazing out the window alerted him to the wayward blimp.

Jarinko estimates the blimp passed about 200 to 300 feet above the tree line, dragging a long tether that pulled down power lines and caused the school's lights to flicker and eventually fail.

NORAD said it worked closely with the Federal Aviation Administration to keep commercial airlines informed of the blimp's location to avoid any close calls.

NORAD said it was still trying to determine how the blimp got loose. Officials said the tether was within weather design minimums when the blimp became detached.

The JLENS system uses two aerostats, or tethered blimps that carry radar equipment — one is used for fire control radar and one for wide-area surveillance radar, NORAD said. The blimps are supposed to fly at up to 10,000 feet.