WASHINGTON PARISH, La (FOX44) -
Update: Today, officials say more fish are dying and it could be weeks before a cause is pinpointed
Authorities are conducting tests to determine what triggered a fish kill on the Pearl River in and around Washington Parish.
Thousands of dead fish floated to the surface of the river in Louisiana and Mississippi.
Some area residents are reporting an unusual substance on the water, which they believe may be related to the fish kill.
Officials in both states are conducting tests to determine if there is a connection.
State officials say a lower amount of oxygen in the water may be to blame.