The lead detective in the case of the raining birds loaded her car with boxes of the dead creatures on Monday, taking them for shipment to a national laboratory in the hope that tests would reveal why thousands of birds suddenly fell from the sky upon the small town of Beebe, Ark.

In the middle of the New Year revelry, as many as 3,000 red-winged blackbirds, common grackles, and European starlings – which often flock together in winter – rained out of the skies, a seemingly Hitchcock-esque phenomenon that scared local residents and prompted concerns about a possible toxic event.

"This was very traumatic for a lot of people. It was very scary," says Arkansas state ornithologist Karen Rowe, talking via cellphone while on her way to ship the birds' bodies to an ornithology lab at the University of Wisconson-Madison. "There were a lot of people who ... witnessed the birds falling from the sky, and since it was New Year's Eve night, it lent some questions to whether there was foul play."

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Early tests on the birds showed no toxic gases trapped in their feathers, though biologists found some physical trauma indicative of being hit by hail or lightning. Still, a bird die-off of this magnitude is unusual. Among the possible explanations: People shooting off fireworks in the area flushed a large roost of birds out of treetops, causing them to fly into either a hail storm or a lightning strike.

Beebe's blackbird population is large enough so that the US Department of Agriculture has in the past attempted large-scale scarecrow techniques to move large flocks out of the area. Outnumbered and outmaneuvered, the USDA gave up those efforts a few years ago.

In 1973, several hundred ducks dropped from the sky near Stuttgart, Ark., known as "The Duck Capital of the World," victims of a sudden storm. In another case, biologists found hundreds of what Ms. Rowe calls "perfectly good," but dead, pelicans in the middle of the woods. While the pelicans showed no outward signs of injury or singe marks, necropsies showed they'd been hit by lightning.

The Arkansas bird mystery seemed especially freaky because it happened all at once and on a night when large numbers of people were outside watching fireworks or traveling home from New Year's Eve parties. Dead birds littered roads, front yards, and rooftops.

Not all of Beebe's residents were alarmed. "Every house cat in Beebe had a New Year's present of delicious blackbird," says Rowe.

Biologists estimate that between 1,000 and 3,000 birds fell over Beebe on New Year's.

Adding to the mystery is an apparent fish kill 125 miles away in the same state. A day before the bird die-off, a tugboat operator near Ozark, Ark., spotted thousands of dead drum fish floating in the Arkansas River. Biologists say the two events are probably not related and suggest that the fish kill – a much more common event than a bird rain – is likely linked to a disease that affected only one species.

Life in Beebe began to resume a sense of normalcy by the end of the weekend, Rowe says.

"The good thing was that it was a single event, it didn't occur again, and once all the birds were cleaned up and nothing else was wrong, most people were comforted," she says.

Arkansas on Saturday morning dispatched its state environmental control crews and a helicopter to survey the damage and to surface test the birds for toxic gases. They found none. If the birds had been poisioned, biologists say, it's more likely that they would have died around their roosts rather than in a single raining event.

What's more, red-winged blackbirds are short-lived birds, so it is not unusual for dozens to die during a single night, falling from their roosting trees. In such cases, scavengers quickly dispose of the dead birds, leaving few traces.

"If there's any real hope of the mystery being solved, it's contained within the bodies of the birds," says Rowe. "There is a potential that [labs] might not find what happened, which is a reminder that mother nature has a way of letting us know who's in charge, by giving us these little mysteries."