WASHINGTON — A massive underground transformer fire in downtown D.C. six days ago caused the closure of L Street between 19th and 18th Streets NW, but as of 6 a.m. Monday one lane was open.

Repairs were winding down Sunday night, just in time for the Monday morning rush, said Pepco spokesman Marcus Beal.

“We’ll have crews and equipment staged on that street, so we urge people driving through the area to use caution, but there will be two lanes open,” Beal said.

Repairs are expected to be complete by noon Monday, Beal said. Multiple transformers were replaced and installed due to the fire that caused 100 customers to lose power.

“All of these customers have been restored from that transformer fire … except for one large commercial building in that area,” he said. “We expect to have that one remaining customer restored by [Monday] at noon.”

Crews have been working around the clock to fully restore power to the area, repair the underground structure, replace the massive transformer and determine the cause of Monday night’s fire.

“That’s one of the many things we’re working on — is trying to determine that cause,” Vincent Morris with Pepco said.