Authorities say the suburban Philadelphia city of Coatesville has been hit by yet another arson -- the 20th deliberately set blaze of the year.

The fire struck two homes around 1:30 a.m. Saturday. Firefighters say both houses were badly damaged.

John Hageman of the federal Bureau of Alcohol, Tobacco, Firearms and Explosives says the blaze was deliberately set.

Click here to see photos.

He declined to elaborate on how the task force determined the fire to be arson.

A 19-year-old man was held for trial Friday in connection with nine blazes between Jan. 2 and Feb. 3, including a massive fire that severely damaged 15 row homes.

Coatesville is a distressed steel town about 35 miles west of Philadelphia.