WINSTON-SALEM (AP) — Officials in a North Carolina city confirmed on Saturday that firefighters responded to a call in late December about a smoldering pile of “fertilizer material” at a plant where, weeks later, an explosion and uncontrolled flames would force thousands to flee their homes.

Winston-Salem firefighters were called to the Winston Weaver Co. plant on Dec. 26, according to an incident report released by the fire department and obtained by the Winston-Salem Journal in response to a public records request.

Nearby residents called 911 and reported seeing haze and smelling smoke in the area around the plant. Firefighters dispatched to the plant noted “a haze coming from the top of the building.”

“Employees at the business met Engine 8, stating that a pile of fertilizer material was smoldering,” the seven-page reports says, adding that the first firefighters inside the building determined there was “no risk of explosion” and flooded the area with water.

The report blamed the incident on an electrical failure which caused machinery to stop operating properly.

“The pile of material was smoldering due to equipment used in the manufacturing process dropping hot materials into the pile,” the report said. “At no point did the pile produce any flames or fire damage.”

Adam Parrish, a spokesperson for Winston Weaver, declined to comment to the newspaper on Saturday.

Rick McIntyre is the lead investigator on the massive fertilizer plant fire that started Monday night. In a Thursday morning briefing, McIntyre said Winston Weaver Co. has had minor fires “within the past couple years.” He said those occurred in electrical equipment. McIntyre did not mention a December fire.

Officials on Thursday also said that the explosion threat from the fire had “greatly diminished” since much of a combustible chemical had burned off, allowing firefighters to return to the site to spray down what’s left.

Residents living in the vicinity of the fire suspected the December fire was a precursor of the most recent event.

“It was just like what we’re smelling now,” said Jarrod Whitaker, who lives near the plant.

When they learned about the potential for a massive explosion at the plant, Whitaker and Wilson Somerville, another nearby resident, exchanged texts in which they recalled the December fire. Somerville said he wants to know if there’s a link between the fire on Dec. 26 and the much larger one on Monday.

“As you can imagine, I and other neighbors wish a very thorough investigation not only of the current fire, but of the previous fire, and given the two fires, a thorough check of whether there was an issue at the plant that had been going on a while,” Somerville wrote in an email.

On Saturday, Winston-Salem city leaders warned the public to stay out of creeks downstream from the plant and to keep pets and other animals out of the creeks due to elevated levels of chemicals in the water resulting from the fire.