The thousands of blackbirds that plummeted to their deaths in front of horrified New Year revellers in Arkansas may have been sent into their deadly spirals by fireworks, raining onto rooftops and into fields as Beebe residents enjoyed the midnight celebrations.

But that doesn't explain why more than 500 birds dropped dead from the sky in Louisiana on Monday or why a Kentucky woman found dozens of dead birds in her yard.

And just a 100 miles away from Beebe's mass bird kill, at least 83,000 dead and dying fish washed ashore, and possibly as many as 100,000.

Louisiana state biologists are trying to determine what led to the deaths of the hundreds of red-winged blackbirds and starlings on highway La. 1 on Monday.

The bird carcasses were lying with many clumped in groups, some face down, some with wings outstretched.

They were found about 300 miles away from the thousands dead in Beebe, Arkansas.

Necropsies are being performed and samples are being sent to multiple institutions for disease testing.

And in Kentucky a woman told a local television station she found dozens of dead birds in her yard on Monday.

It is unclear what if anything is happening with the Kentucky carcasses.

Up to 100,000 dead and dying drum fish washed up along a 20-mile stretch of the Arkansas River, about 100 miles west of Beebe.

Wildlife officials say the fish deaths are not related to the dead birds, and that because mainly one species of fish was affected, it is likely they were stricken by an illness.

Had it been an environmental cause, other kinds of fish would be dead, too.

Full test results on the fish could take up to a month.

A little further north the Maryland Department of the Environment said that tens of thousands of small fish have died in the Chesapeake Bay.