The New York Times reported March 20 that state and federal authorities are investigating whether several New York heating oil businesses cheated customers for years by selling fuel diluted with recycled or waste oil. Burning waste oil in furnaces could present a significant environmental hazard.

As part of the criminal investigation, the Times said, authorities March 12 raided at least five heating oil businesses in and around the city, including a delivery company and several businesses that deal in waste oil and some that are licensed to recycle it. Two days later, several commercial and residential building owners filed two lawsuits, seeking class-action status.

During the raids, investigators from several state, city and federal agencies — some wearing bright yellow head-to-toe protective suits — tested oil and seized computers, reams of records and other materials, the Times reported. They will examine transactions involving hundreds of millions of gallons of oil, some dating as far back as 10 years.