Cleanup efforts at a Sterling Drug dump have turned up at least 6,500 barrels of waste, making it the biggest such cleanup in the state, a state official said Wednesday.
The number is more than three times Sterling's first estimate.
But the barrels' contents will have to be tested to determine if they pose a greater environmental threat than first suspected, said Ben Marvin, a state Department of Environmental Conservation spokesman.
"This is certainly the largest barrel-removal project in the state to date," Marvin said.
"Whether this makes it the worst or most expensive or most dangerous depends on whether those drums contained anything."
The barrels could contain old clothes or rags, which would not pose the hazard that contaminated liquids might, he said.
Sterling began digging up the barrels last fall on a site along the Hudson River opposite Albany.
The pharmaceutical firm buried the drums in the 1950s and 1960s.
The most common chemicals buried there are the solvents benzene, diethyl ether and toluene.
Benzene, the most dangerous, can cause leukemia.