Colorado fire authorities are probing a series of suspicious fires, including one that killed a half-dozen horses.

In a written statement the West Metro Fire Rescue, in Lakewood, Colorado, said crews responded to four fires near Lakewood on April 28. Three of the blazes occurred within a block of each other, including a fire in a barn containing 10 horses. Four horses were rescued from the barn, but the remaining six lost their lives. The fourth fire occurred just over a mile away from the other three.

The fires have been ruled suspicious due to their proximity to one another, the statement said.

The Lakewood Police Department, the Colorado Bureau of Investigation, and the Denver branch of the Bureau of Alcohol, Tobacco, Firearms, and Explosives are also investigating the fires, the statement said