KITCHENER, Ontario - Was it a planet? A plane? A meteorite? Little green men?

Whatever it was, residents across Waterloo Region saw something unusual in the night's sky yesterday. Around 8 p.m., the calls started coming into police stations, describing a fiery display streaking across the horizon.

Some, worried they were witnessing a falling airplane, phoned authorities, who set off on a search and rescue that turned up nothing. Local airports reported no downed planes last night.

In the span of a few minutes, multiple calls came in from St. Clements to Cambridge, said Sgt. Sharon Havill of the Waterloo regional police.

"We did some searching around," she said. "We don't have an answer for sure as to what they were. There were definitely multiple callers, saying they saw a flash in the sky. They weren't sure whether it was a helicopter or whether it crashed."

At one point, the calls had some police officers joking about searching for "little green men."

Police in Guelph had calls about the sightings, too. They promptly phoned the OPP to go check it out, said Sgt. Neal Young.

"It was on the west side of town, something like flames falling from the sky."

Marie Keyes was driving home along Weber Street with her husband when she saw what she initially thought was a shooting star or fireworks. When she looked closer, she saw an object with a trail of sparks arching toward the ground.

"I screamed 'look at that!'" she said. "It was amazing. It was such a shock when it came into view in my windshield. It kind of like dropped.

"It was too low to the horizon, and too large, to be a shooting star. I saw a blue flame coming out the end, and it had a tail, with sparks. It was moving very fast, it was a huge ball. And then it just sort of burned out."

About 15 minutes earlier, in the parking lot of a Victoria Street restaurant, Keyes and her husband saw bright moving lights that passed overhead.

These rectangular-shaped objects moved "unusually" and didn't look like "a typical airplane," she said.

Darryl Archer, an amateur astronomer and a member of the Kitchener-Waterloo Centre of the Royal Astronomical Society of Canada, said he didn't see anything unusual from his observatory last night. But on such clear winter nights, it's not uncommon for people to mistake the planet Venus for something far more exciting, he said.

"It's the brightest object in the sky next to the sun and moon, so some people mistake it for a UFO," he said from his home in Baden.

He said no meteorite showers were expected last night.