More strange lights were seen in the skies over Maine late Thursday night, but it’s unlikely they were related to an incident earlier this week.

An Air Force spokeswoman said Friday that the sighting of “fireballs in the sky” off Maine’s coast Monday evening was almost definitely part of a U.S. Air Force booster rocket.

Between 10 and 11 p.m. Thursday, Bangor police and Penobscot County sheriff dispatchers received several calls describing shafts of yellow and white light that extended from the ground to the sky. Additional sightings of an orange glow over northern Penobscot County also were reported.

A meteorologist with the National Weather Service in Caribou said there was no meteorological explanation for the lights. Rebecca Hupp, director at Bangor International Airport, said the airport did not field any calls overnight Thursday.

On Monday evening, reports flooded dispatch centers in Washington County and New Brunswick describing strange orange lights in the sky. At first there was concern that a plane had crashed in the Bay of Fundy, but a quick search by the U.S. Coast Guard revealed that was not the case.

Air Force Lt. Col. Maria Carl confirmed Friday that the Air Force launched an Atlas V booster shortly after 5 p.m. Monday from Cape Canaveral Air Force Station in Florida. It was carrying what she called National Reconnaissance Office payload, but she didn’t elaborate because it was a classified mission.

Ten minutes after the booster was launched north, an expendable fuel tank separated and dropped into the Atlantic Ocean about 100 miles off Nova Scotia, she said.

“Obviously, I don’t know for sure what people saw, but based on the trajectory and the timing, it seems accurate that it would have been the booster,” Carl said Friday.

While her explanation might close the door on Monday’s sightings, it doesn’t explain the reports of orange and yellow light shafts seen Thursday.

“I can’t speak to that,” the Air Force spokeswoman said, “but we didn’t have any additional launches, so that wasn’t us.”

Neil Comins, an astronomy professor at the University of Maine, said Thursday’s light show could have been several things. For example, a variety of gases glow in the atmosphere.

“It’s entirely plausible that what people saw last night was frozen residue [from the gases] that re-entered the atmosphere,” he said.

Comins did not rule out the possibility that Thursday’s sighting was related to the incident from Monday.

“There is a slim but not negligible possibility that something in orbit could have decayed at a slower rate,” he said, referring to the Air Force launch.

While strange reports of lights in the sky occur several times a year, Comins said, it’s uncommon to see two reports in the same week.

“So, in that sense, I can’t say, ‘No, they are definitely not connected,'” he said.

The lack of a conclusive explanation for either incident this week has conjured up memories of an incident that was reported 40 years ago in waters off Nova Scotia.

The “Shag Harbor Incident,” which occurred Oct. 4, 1967, is one of the most-documented potential UFO sightings in history.

Similar to Monday’s incident, residents of the small Nova Scotia fishing village of Shag Harbor saw unusual orange lights in the sky. After that, others saw an object descend toward the water, but instead of crashing into the ocean, it hovered on the surface, according to reports by MUFON, a large organization that investigates reports of unidentified flying objects.

The Bangor Daily News reported that residents of Washington County and elsewhere in Maine reported strange lights in the sky the same night.

The Shag Harbor Incident was investigated by the U.S. Coast Guard, and some reports indicate that an unsuccessful search was conducted.

Because the sightings could not be attributed to any military or civilian launch, the incident quickly gained infamy.

Carl didn’t comment on the Shag Harbor Incident but she said that anytime the Air Force launches a booster, her office gets numerous calls, so she wasn’t surprised this week.