Arkansas game officials hope testing scheduled to begin Monday will solve the mystery of why more than 1,000 blackbirds fell from the sky just before midnight New Year's Eve.
The birds -- most of which were dead -- were found within a one-mile area of Beebe, about 40 miles northeast of Little Rock, the Arkansas Game and Fish Commission said.
As of Saturday, between 4,000 and 5,000 blackbirds had been found dead, said Keith Stephens with the commission.
Karen Rowe, an ornithologist for the commission, said the incident is not that unusual and is often caused by a lightning strike or high-altitude hail.
A strong storm system moved through the state earlier in the day Friday.
Officials also speculated that fireworks shot by New Year's revelers in the area might have caused severe stress in the birds. Rowe said Sunday there was evidence that large fireworks may have played a role.
Biologists believe the deaths were stress-related from either fireworks or weather, Stephens said.