Workers inspect an area outside a retaining wall around storage tanks where a chemical leaked into the Elk River at a Freedom Industries storage facility in Charleston, W.Va., Jan. 13, 2014. Steve Helber/AP Images

The company behind a West Virginia chemical spill that contaminated the water supply of 300,000 people now estimates some 10,000 gallons of chemicals, up from an earlier figure of 7,500 gallons, were involved in the leak, state regulators said Monday.

West Virginia's Department of Environmental Protection released the new figure Monday from Freedom Industries regarding the scope of a Jan. 9 leak from a plant in Charleston. The agency emphasized it's still unknown how much of the leaked chemical mix, including a coal-cleaning agent, actually spilled into the Elk River.

Residents in nine counties had to stop using tap water for days, except for flushing toilets.

DEP Secretary Randy Huffman said the revised estimate was in response to a previous order from the state agency about the quantity of chemicals released.

"We are not making any judgment about its accuracy," he said in a release. "We felt it was important to provide to the public what the company has provided the WVDEP in writing. We are still reviewing the calculation, and this is something that will be researched further during the course of this investigation."

Huffman emphasized the independence of the department's remediation efforts.

"Our actions have never been dependent on what Freedom has reported to us. From the start, we have acted aggressively to contain the spill and remediate the site," he said.

After its initial acknowledgment of the leak, Freedom Industries said a second chemical was mixed with the coal-cleaning agent that spilled. The DEP reported that Freedom Industries said it has recovered about 1,272 gallons of the chemical mixture at the plant.