TOLEDO, Ohio (AP) -- Fire officials say they are investigating the causes of five house fires that occurred within the space of about four hours in a northwest Ohio city.

The Blade ( http://bit.ly/MdDPmq ) reports that fire officials say they do not know whether any of the fires in Toledo Sunday morning were related. Toledo fire Lt. Matt Hertzfeld says the only injury was to a firefighter who was treated at a hospital and released.

The blazes left at least four families homeless, including 13 children. One of the houses was unoccupied.

The first fire occurred about 1 a.m. with the last one reported shortly before 5:30 a.m.

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Information from: The Blade, http://www.toledoblade.com/