A mysterious purple plume that rose above the Portland skyline Thursday morning was most likely caused by a larger-than-normal amount of iodine in the waste stream at ecomaine’s waste to energy plant, company officials said.

The purple plume, tinged with pink, began rising from a stack at the plant on Blueberry Road in Portland around 9:20 a.m. and could be seen as far away as the Maine Mall in South Portland, the Portland International Jetport and the Maine Turnpike.

Ecomaine in Portland. Shawn Patrick Ouellette/Staff Photographer

Ecomaine employees fixed the problem in a couple of hours and normal operations resumed, according to a statement from the waste to energy plant. Ecomaine burns solid waste from 73 communities to produce electricity.

“This was probably caused by a larger than normal amount of iodine present in the waste stream all at once,” ecomaine CEO Kevin Roche said in a release. “Fortunately our plant employees were able to correct the situation in 2.5 hours and get the plant back to normal operations.”

Ecomaine said that it has never experienced a similar problem before, but other waste to energy facilities around the nation have. The colored vapor in those instances was linked to iodine entering their combustion chambers.

Iodine is commonly used in pharmaceuticals, disinfectants, inks, animal feed supplements, and photographic chemicals. Vaporized iodine can pose health risks if inhaled directly. But ecomaine said it was unlikely that anyone had direct exposure “due to the relatively short time the incident occurred and its location.”

According to the U.S. Centers for Disease Control and Prevention, short-term exposure to iodine can irritate the eyes, respiratory tract and skin.

Ecomaine said the incident reminds municipalities of the importance of ensuring their solid waste is disposed of according to state and federal standards.

A spokesman for the Maine Department of Environmental Protection was unavailable Thursday to answer questions about the incident.