UPDATE: 6 p.m.

The fire has been struck, according to Lt. Andy Veath, of the Cary Fire Protection District.

Assisting fire crews are beginning to leave the scene. Investigation efforts likely will begin tomorrow morning, Veath said, because of nightfall and the lack of light.

No further information was available regarding the condition of those injured, the cause of the fire and how much damage the building sustained after burning for nearly five hours.

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UPDATE: 4:45 p.m.

The incident remains "an active fire scene," according to the Cary Fire Protection District. All assisting fire departments remain on scene.

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ORIGINAL STORY: Posted at 2:11 p.m.

Firefighters are on the scene of a blaze at Fox Valley Systems, 640 Industrial Drive in Cary.

As of 2:45 p.m., "foam" and Hazmat Materials Units were being called in to help fight the fire, which is being fueled by paint and chemical products. Officials on the scene said the only way they expect to extinguish the fire is with foam.

An explosion started the blaze at about 1:15 p.m. Wednesday, said Cary Police Chief Steve Casstevens, who watched as several area units battled the blaze. 

"We responded to the scene because of the initial explosion, but once responders were here, there was a second explosion," Casstevens said.

Three people were injured by the first blast. Two of the injured were  transported to Good Shepherd Hospital in Barrington for treatment. The severity of their injuries is not yet known, he said.

The explosions blew out a front wall of the building, and created a hole in the back wall, he said.

Occupants of the surrounding buildings were evacuated, and police asked Metra officials to slow trains as they past the fire scene, located adjacent to the Northwest Line tracks and Route 14.

As white and grey smoke billowed from the building, fire trucks from a multitude of area fire departments lined Industrial Drive. From atop ladder trucks, workers sprayed water onto the roof of the building, and other responders appeared ready to assist at the ground level.

Casstevens said officers from 15 area law enforcement agencies were on the scene, as well.

Police were directing traffic along Cary-Algonquin Road, which intersects with Industrial Drive. The traffic included school buses filled with students. At least four helicopters hovered overhead- appearantly media helicopters as none assisted with the fire fighting efforts.

Fox Valley Systems manufactures paint and equipment used for striping athletic fields, according to the company’s website.

Motorists are encouraged to avoid the area, including Cary-Algonquin Road near Route 14.

Check back to Patch.com for more updates.