The Tulsa, Okla.-based firm said the company has completed an expansion and the plant has begun manufacturing ethylene, a key component in making chemicals.

The expanded plant will be able to make 1.95 billion pounds of ethylene a year. Williams was close to completing the expansion, which added 600 million pounds of production capacity, when the explosion occurred.

Williams has paid a little more than $194,000 in fines to the state Department of Environmental Quality for a series of "penalty events" including the fire. The U.S. Occupational Safety and Health Administration also fined Williams $36,000 for violations related to the fire.

John Dearborn, Williams’ senior vice president of NGL & Petchem Services, said ethylene production is a key milestone.

“We will now turn our efforts to reaching full production rates on the base plant and shortly thereafter ramping up the plant to the expanded production capacity of 1.95 billion pounds of ethylene per year,” Dearborn said.

The company also looks forward to "rebuilding our reputation as a safe and reliable supplier of olefins,” Dearborn said.