A tornado with winds of about 105 mph struck Garyville early Wednesday and damaged a cooling tower at Marathon Petroleum’s refinery, officials said.

The National Weather Service confirmed that a tornado was responsible for the damage, which knocked out power at part of the facility, including one of its crude units, said Jamal Kheiry, a Marathon spokesman.

Damage assessments were ongoing Wednesday, he said.

“It is likely that this crude unit will remain shut down until repairs are made to the cooling tower,” Kheiry said. “Once we determine the time frame for repair, we will have a better understanding of the production impact. The refinery continues to operate the second crude unit and other units.”

The weather service said initial storm estimates pegged the tornado at an EF-1, based on the Fujita tornado damage scale.

“We have made notifications to the appropriate local and federal agencies. There has been no off-site impact,” Kheiry said.

Response crews from the Louisiana Department of Environmental Quality were at the refinery Wednesday morning inspecting damage and conducting air monitoring, said spokeswoman Jean Kelly, who also reported no initial off-site impact.

Kelly said the refinery was experiencing “significant flaring,” a sign that one or more units were not functioning properly.

“It usually means that things are not functioning correctly, and the flare is a safety mechanism to burn off anything that’s being emitted,” she said.

Meteorologist Mike Hill said the tornado likely hit between 5:30 a.m. and 6 a.m.

About 5:30 a.m., storm radar showed 105-mph winds moving through Edgard and across the Mississippi River into Garyville, downing trees, damaging roofs and knocking out power, said Paige Falgoust, a St. John the Baptist Parish spokeswoman.

The bay doors of the fire station in Edgard were damaged, Falgoust said. Areas along the east bank of St. John Parish, including Garyville and Reserve, got up to 8 inches of rain, while more than 3 inches of rain was reported in Edgard.

Power had been restored to all but about 40 customers by 1 p.m., according to Entergy Louisiana.

Follow Richard Thompson on Twitter, @rthompsonMSY.