Ohio River Valley Water Sanitation Commission (ORSANCO) says the chemical, MCHM, is no longer detectable in the Ohio River.
ORSANSO says it monitored the Elk River spill along the Ohio River until it reached the Mississippi River.
MCHM was last detected on Saturday in Louisville.
A storage tank in Charleston, West Virginia, leaked MCHM on January 9, contaminating the city's water supply.
MCHM is a chemical used in coal processing.