Dozens of dogs were killed after a fire erupted at a Chicago-area kennel Monday morning.

The fire at D&D Kennels was first spotted at about 5:30 a.m. Monday by a sheriff’s deputy on patrol.

When firefighters arrived, they found the two-story building – which had attached dog kennels on either side – engulfed with flames shooting out of the second-floor windows, the Carol Stream Fire Protection District said in a statement.

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The building was housing approximately 50 pitbull rescues. A number trapped in cages in the main building died. At least 25 of the dogs were rescued.

Kennel operator Garrett Mercado told reporters that he injured his hands on the hot metal cages that housed some of the dogs he tried to save.

“I was just opening as many doors as I could, hoping they would follow me out,” he said, according to the Chicago Tribune.

Three firefighters suffered minor dog bites, the district said.

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Carol Stream Fire District Chief Bob Hoff described it as “a very, very sad scene.”

A spokeswoman for the Illinois Department of Agriculture, which licenses dog kennels, told the Tribune that D&D had an up-to-date license.

The DuPage County Fire Investigation Task Force is investigating the cause of the fire, which authorities say doesn’t appear to be suspicious.

The Associated Press contributed to this report.