HOPEWELL, Va. -- State and federal agents conducted a raid at the AdvanSix in Hopewell Tuesday morning, along with the US Postal Inspector police.

Virginia State Police, FBI agents, EPA investigators, and the Virginia Department of Environmental Management were seen at the AdvanSix’s Hopewell facility, according to witnesses.

AdvanSix is a spin-off of Honeywell International. The company previously paid a $3 million civil penalty for alleged Clean Air Act violations at its Hopewell, Va., plant. According to the complaint filed by EPA and the Virginia Department of Environmental Quality, the facility violated Clean Air Act limits on emissions of nitrogen oxide (NOx), benzene and other volatile organic compounds (VOCs), and particulate matter. The plant also allegedly failed to comply with requirements to upgrade air pollution control equipment, to detect and repair leaks of hazardous air pollutants, and to develop safeguards on benzene waste.

As part of that case, Honeywell agreed to reduce harmful air pollutants, install selective catalytic reduction at four production trains at the facility, conduct third-party benzene waste operations audit, and implement enhanced leak detection and repair program at the facility. The settlement was intended to reduce annual emissions of NOx by about 6,260 tons, and cuts annual emissions of benzene, other VOCs and hazardous air pollutants by 100 tons, according to the EPA.

The facility was last inspected by the EPA on Sept. 19, 2017 and a significant violation was uncovered. Three months earlier the same facility was found in noncompliance.

"This is a non-violent situation," AdvanSix spokesperson Debra Lewis said when asked about the investigation. "AdvanSix intends to fully cooperate with law enforcement. All of our employees, contractors and visitors are safe, and the Hopewell plant continues to operate normally."

The AdvanSix plant in Hopewell is "one of the world’s largest single-site producers of caprolactam," according to the company's website.

Caprolactam is used to make carpet fibers, plastics and films.

"Hopewell is a global leader in the development and production of ammonium sulfate fertilizers, which AdvanSix sells for both crop and turf applications under the Sulf-N® brand," the website description continued.

More than 750 people work in the Hopewell facility. Employees were told not to use their computers, according to sources.

The other AdvanSix facility in Chester has also been found in noncompliance. As recently as January 2018, the facility was found to have surpassed the maximum allotment for total organic carbon in wastewater discharge, for the fourth time since August 31, 2016, according to EPA data.

This is a developing story. Witnesses can send news tips and photos here.

Full statement from AdvanSix Inc.

AdvanSix is cooperating fully with the federal and state investigators who visited our Hopewell site today. Everyone at the plant is safe, and we have no information leading us to believe that the facility's operations will be affected in any way. The plant is operating normally and we have every intention to continue to operate as planned.