WELD COUNTY, Colo. (CBS4)– Crews worked to keep contamination out of nearby farms and irrigation ditches after tanks at a fracking wastewater facility in Weld County burst into flames on Friday afternoon.

The explosion happened about 1 p.m. at the site located near the intersection of Weld County Road 47 and Weld County Road 64, just northeast of the Greeley Airport.

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Workers at a storage and injection well site northeast of the Greeley-Weld County Airport said lightning sparked the fire, and for a while the flames were too dangerous for crews to attack.

(credit: CBS)

(credit: CBS)

Fracking wastewater, which does contain some petroleum, is stored at the site.

Firefighters were forced to watch at tanks exploded.

“It’s vapor that gets heated up in those tanks and as things heat up, they expand and create internal pressure in the tanks,” said Greeley Fire Department Fire Marshal Dale Lyman.

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The fire burned for nearly five hours. Three homes were evacuated near the fire but no injuries were reported.

“We were concerned that radiant heat may ignite the trees and maybe the house,” said Lyman.

(credit: CBS)

(credit: CBS)

Lyman said the flammable fluid contained inside each tank is what remains after drilling, a mix of mostly water, crude oil and chemicals. It’s taken to the tanks where crews separate the water and oil and re-inject it into the ground.

Crews built a dam to try to contain the runoff from the fire, hoping to keep the contaminated water from reaching nearby farms and irrigation ditches.

Crews said on Friday night it was too soon to tell how much of the fracking wastewater seeped into the ground or if it got into irrigation ditches and farmland.

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CBS4 was not able to reach the site’s owner, NGL, for comment.