ST. PAUL, Minn. (AP) -- State pollution officials say the owners and operators of the St. Paul District Heating operation have paid a civil penalty of $55,000 to resolve allegations of air-quality violations.

The Minnesota Pollution Control Agency announced the agreement Friday.

Three companies are Ever-Green Energy LLC and two affiliates: St. Paul Cogeneration LLC and District Energy St. Paul Inc. The fourth is Environmental Wood Supply LLC.

The companies' air-quality permit allows for a certain level of carbon-monoxide and nitrogen-oxide emissions. The agency says the companies exceeded those limits between 2008 and 2010.

Ever-Green spokeswoman Nina Axelson says the company and its affiliates have corrected the problems and are cooperating with MPCA. A message left with Environmental Wood Supply was not immediately returned.