An oil storage tank on a well pad lies toppled by floodwaters in Weld County. Environmental activists have raised concerns about leaks of gas, oil and hazardous materials from compromised infrastructure. Rick Wilking/Reuters

As Colorado reels from a prolonged flooding disaster that has killed at least eight people and left hundreds unaccounted for, environmental groups warn of potential contamination by ruptured oil and gas industry infrastructure.

In Weld County, which has seen some of the worst of the rains, activists point to photos of destroyed wells, tanks and pipelines posted on social media sites. They claim that years of “fracking,” the process of drilling for shale gas through hydraulic fracturing, has made the area northwest of Denver and Boulder vulnerable to contamination in the event of flooding.

"Weld County, where the South Platte River has been flooding uncontrollably, has almost 20,000 active oil and gas wells," Gary Wockner, Colorado program director for Clean Water Action, told Al Jazeera.

"It's the most heavily drilled county in the U.S., and it's seeing some of the worst flooding," he said. "Oil and gas and chemicals associated with drilling are going to be spread across a wide swath of landscape."

The latest flood began last Wednesday, triggered by unusually heavy late-summer storms that drenched the northeastern part of Colorado. Along with Weld, the counties of Boulder, Adams, Jefferson and Larimer have been the worst hit.

There are hundreds of active oil and gas wells built in the South Platte River floodplains alone that are at risk of contaminating the floodwaters. Already there have been reports of a ruptured natural gas pipeline and overflowing crude-oil wells. By Wednesday evening, the Denver Post was reporting that crews had placed absorbent beams into the South Platte River south of the town of Milliken, where it said 5,250 gallons of oil had spilled into the river.

Ahead of that news, industry representatives had attempted to downplay any risk, suggesting that the pictures of broken pipes and underwater wells amount to a “social media frenzy.”

Tisha Schuller, president of the Colorado Oil and Gas Association, testified before the Colorado Oil and Gas Conservation Commission regarding the industry's response to the historic floods, which have forced the evacuation of more than 10,000 people.

"All impacted wells have been shut in, which means the well has been closed off or shut and is not producing any oil and gas product," Schuller said in a release.

Schuller also responded to controversial photos that Colorado residents have uploaded to social media sites showing floating tanks, blowouts and flooded infrastructure.

"We have seen the social media frenzy regarding pictures of oil and gas facilities 'under water,'" she added. "While the pictures seem extraordinary, there is no data or specifics provided."

The photos and videos have not been independently verified by Al Jazeera.

Wockner, meanwhile, said he had seen "a number of photos online that show wells underwater and big tanks either floating or toppled," and that the risk of contamination is real.

"These containers have pipes attached to them and can hold 5,000 gallons or more," he said. "If the tank is floating and tilted, then the pipes are probably breaking off."

Possible contaminants from fracking include toxic chemicals, including cancer-causing benzene, activists point out.