BATON ROUGE, La. (AP) — ExxonMobil says the benzene release June 14 at its chemical plant in Baton Rouge was far bigger than the 10 pounds reported then, and could be as much as 28,700 pounds.

That estimate is in a required report to the state Department of Environmental Quality about the spill of naphtha, which contains benzene.

The Advocate reports that DEQ began an investigation Thursday, one day after getting the report.

Assistant Secretary Cheryl Nolan says part of the investigation is finding out when ExxonMobil Chemical Plant officials learned how much bigger the spill actually was.

Inspection division administrator Chris Piehler says initial estimates of releases are usually inaccurate as facilities work to get information out fast. But he says companies must report changed estimates as they learn them.