Smoke and flames from two tanks of burning crude oil at a Denbury Resources storage facility were largely extinguished around 5 p.m. Friday, though responders continued to battle occasional flare-ups in one of the tanks.

Residents who had been evacuated late Thursday night from about 30 homes within a 1-mile radius of the tanks were allowed to return to their homes Friday evening, with the exception of a few households closest to the site, said Mark Harrell, director of the Livingston Parish Office of Homeland Security and Emergency Preparedness.

State Department of Environmental Quality spokesman Rodney Mallett said Friday afternoon that air quality monitoring both at the site and in the community had detected no elevated levels that would pose a health risk.

An oil tank explosion shortly after 10 p.m. Thursday southeast of the intersection of Linder and Arnold roads, between Denham Springs and Watson, touched off a fire that later spread to a second oil tank.

No one was hurt in the explosion, Harrell said, but the homes were evacuated out of an abundance of caution.

Residents described the explosion as a loud boom, much like a thunderclap accompanying the storms that swept through the area around the same time.

While authorities were investigating the cause of the explosion, residents living across the street from the site reported seeing several lightning strikes in the vicinity just before the explosive boom.

Donald Davidson said he believed the explosion was thunder until a picture fell off his wall. Then he knew the sound must have been something else.

One of Davidson’s neighbors, who lives closer to the tanks, initially thought a tree had fallen on his home, Davidson said.

The fire blazed for hours Friday, until responders were able to inject a fire suppressive foam into the bottom of the second tank starting around 3 p.m. The fire in the first tank was nearly out by that point.

An earlier plan to spray the foam on the flames and use vacuum trucks to keep it from overrunning the containment area was abandoned after a 45-minute discussion among responders about the best course of action.

While the flames were largely extinguished by 5 p.m., one tank continued to flare up sometimes, its temperature staying around 350 degrees Fahrenheit, Harrell said.

Linder Road residents living between White Oak Trailer Park and Arnold Road were being asked to stay away from the area Friday evening until the remaining hot spots could be dealt with and the second tank’s temperature dropped to about 100 degrees.

“It will continue to flash off and on for a while. That’s just the nature of the beast,” Harrell said. “I couldn’t begin to speculate how long that section (of Linder Road) will remain closed.”

Denbury Resources has offered to pay residents’ out-of-pocket expenses caused by the evacuation, said Jack Collins, spokesman for the Plano, Texas-based oil and gas company.

The two tanks, which held crude oil from the Denbury-operated oil field at Lockhart Crossing, each have the capacity to hold about 2,000 barrels, but are believed to have been only half-full before the fire, Collins said.

The flames had reached heights of 30 to 35 feet Thursday, and the fire encompassed about a 200-square-foot radius. The oil was contained in a 50-foot berm, which is standard procedure for this type of incident.

Denbury had a private crew leading the firefight with assistance and backup from Livingston Parish Fire District No. 5 and other area responders.

Denbury Resources is the largest oil and natural gas producer in Mississippi and Montana, with significant operations in the Rocky Mountain and Gulf Coast regions, according to the company’s website.

The company specializes in the recovery of played-out oil fields, injecting carbon dioxide into the ground to remove oil that couldn’t otherwise be extracted.

Denbury first announced plans for reviving old wells in the Lockhart Crossing area near Denham Springs in 2007.

The oil storage and loading facility off Linder Road has been in service for several years.

Advocate staff writer Ryan Broussard contributed to this story.