PHOENIX - State of Arizona and Maricopa County air quality crews monitored the air near a transformer fire that broke out in north Phoenix.
Phoenix Fire Department Capt. Scott Walker said about 35,000 gallons of mineral oil used for cooling, enough to fill two swimming pools, was burning inside one of nine transformers sitting on the ground inside a power substation owned by Arizona Public Service.
"We had a transformer at one of the APS substations burst into flames," Walker said. "We don't know what caused it."
According to a Tuesday morning tweet from the Phoenix Fire Department, crews planned to let the fire burn out because if they put too much water on the flames, they would risk the oil overflowing into neighboring homes.
The Department of Environmental Quality determined the black plume from the transformer fire was nontoxic and posed no health hazard to the public.
"Atmospheric conditions appear to be good for that remaining like that for the rest of the afternoon so that part's been good," said Mark Shaffer, spokesman for the Arizona Department of Environmental Quality.
Shaffer said what was burning is generally found products such as laxatives with little chemical compound.
Holly Ward, a spokeswoman for the Maricopa County Department of Air Quality, said Tuesday the smoke plume was rising and traveling to the west and southwest.
Shaffer said schools near the fire were also made aware of the smoke in case conditions changed.
There were no evacuations with the nearest home about a mile away.
The fire started around 10 p.m. Monday at the facility near Pinnacle Peak and Scottsdale roads.
Fire officials said no homes or businesses lost power due to the fire.