Authorities say all of the fires reported early Saturday have been ruled arsons.
A spokesman for the federal Bureau of Alcohol, Tobacco, Firearms and Explosives says the investigation is continuing and there have been no arrests.
The ATF spokesman, John Hageman, says Saturday's fires share "a commonality" with the blazes already under investigation. But officials aren't sure if they are connected.
On Jan. 24, the most destructive blaze ripped through a block of row houses in Coatesville, heavily damaging 15 homes.