More than a foot of rain fell on parts of Colorado last month during what the National Weather Service described as a "biblical" weather event.
The Colorado Oil and Gas Conservation Commission said it has been able to confirm at least 600 barrels of oil were spilled in the flooding.
The Denver Post reported Sunday state regulators were slow to respond to initial issues at oil and natural gas operations in the state.
Alan Gilbert, a director at the Colorado Department of Natural Resources, told the Post state regulators were examining their response to last month's disasters.
"We are going to have a formal review," he was quoted as saying Sunday. "We'll look at what worked and what didn't work."
State regulators downplayed reports the oil and natural gas contamination was out of control. Bruce Baziel, director of advocacy group Earthworks, suggested state authorities were absent during the crisis.
"Did the state have a disaster plan for the oil and gas fields?" he asked. "It was hard to tell."