Anthrax has been ruled out.
Officials at the GE Motors plant on Hodgesville Road called police and fire personnel after a mysterious white powder showed up in a parts shipment.
The plant was evacuated and reportedly nine employees were taken to a Dothan hospital for examination.
A sample of the powder was sent to Auburn University in Montgomery for testing.
Officials say it is not anthrax, but could be some other hazardous substance.
Police Chief John White says the plant could remain closed until Saturday afternoon as testing on the unknown substance continues.