Valero Energy Corp., the third-largest U.S. ethanol producer, has restarted distilleries in Nebraska and Indiana, as profit margins for the fuel improved.

San Antonio-based Valero halted the operations in Albion, Neb., and Linden, Ind., in June, citing unprofitable returns. The Linden plant, about 50 miles northwest of Indianapolis, has about 60 employees who continued to work on maintenance during the shutdown.

The company is now operating all 10 of its plants, with the capacity to produce 1.2 billion gallons of the fuel annually.

“Ethanol margins improved to the point where it became feasible to operate the plants again,” Bill Day, a company spokesman, said in an e-mail. “We had said when we closed the plants down temporarily in June that we expected them to be back in operation during the harvest.”

The Agriculture Department said that 26 percent of the corn harvest was completed as Sept. 16, up from 15 percent a week earlier.

Poet LLC in Sioux Falls, S.D., is the largest U.S. ethanol producer, followed by Archer Daniels Midland Co. in Decatur, Ill.