Two firefighters were injured Wednesday after a vacant gas station holding 90,000 pounds of chemicals went up in flames in northwest suburban Park Ridge.

The fire was first reported about 5 p.m. in the 900 block of North Northwest Highway and took about an hour to put out, Park Ridge Fire Chief Jeff Sorensen said.

However, towards the end of the firefight, first responders discovered that the building was housing 90,000 pounds of calcium peroxide, which was put there for remediation work on the property, Sorensen said.

Fire crews spent the next several hours attempting to contain the newfound hazardous materials scene as they were dealing with runoff from the chemical, which had reacted to the 250,000 gallons of water used in the firefight, Sorensen said. Most of the responding fire companies left the scene about 10:30 p.m.

The owner of the property called a private hazardous material cleanup crew in order to clear the public streets and sidewalks, Park Ridge fire said. They continued their work into Thursday morning.

Two firefighters, one from the Niles Fire Department and the other from the Schiller Park Fire Department, were treated for minor chemical burns and released from Lutheran General Hospital, Sorensen said.

The Illinois Environmental Protection Agency is working with the owner of the property to develop a plan to minimize the risk of another incident at the site.