A pink and purple plume of smoke that has been seeping out of the Covanta incinerator in Newark is causing some residents to be alarmed.

Pink smoke is generally a sign that Iodine is being burned. Iodine is often found in medical waste and when burned can be hazardous. People who live near the incinerator say that they have spotted the pink and purple smoke for the past five months. The Covanta incinerator is in the east Ironbound section of Newark.

"One day in June - June 21 - we saw it for about four hours. It was burning in the air. Everyone in the community was noticeably alarmed,” says Maria Lopez with the Ironbound Community Corporation (ICC).

Lopez says that medical waste is not allowed to be burned at the Covanta site. In response, management at the facility told the state Department of Environmental Protection that they would have more inspectors looking for such trash.

But those living in the neighborhood don't think that's enough.

“They're supposed to identify trash that's not supposed to be burned. We don't think that's enough of a safety precaution,” says Lopez.

Covanta sent out a message in June that said, "The pink color coming from the Covanta Essex stack is a rare occurrence that can happen when a load of trash is combusted that contains iodine. It's not a danger to the public/the environment. We are actively working with our customers to ensure iodine does not come to our facility."

The ICC sued Covanta in 2009 and forced the company to reduce emissions from the smokestack. The incinerator is the largest in New Jersey. It burns 2,800 tons of trash per day with 40% of that trash coming from New York.

The group is once again fighting the incinerator. Lopez says that the group hopes that the New Jersey Office of the Attorney General looks into how often and how much iodine is coming out of the smokestack.

Covanta's permit is currently under review by the Department of Environmental Protection.