ANCHORAGE, Alaska - An independent oil producer paid a $10,000 fine this week for injecting a chemical without approval into its oil reserve, one violation that came to light after a former employee spoke out against the company.

The Anchorage Daily News reports that Pioneer Natural Resources, the sole independent oil producer on the North Slope, did not challenge the fine leveled by the state.

Pioneer injected 45,000 gallons of glycol, an antifreeze fluid commonly used in oil reservoirs. However, the company had not sought permission from regulators.

The Alaska Oil and Gas Conservation Commission is also investigating other allegations made by former employee Mike Kelley, including that the company covered up spills, injured wildlife and created unsafe conditions for workers.