Washington  - Another four fires discovered early Saturday were blamed on a serial arsonist believed to be responsible for at least 17 torchings since January 1 outside Philadelphia, a local newspaper reported.

Over the past year, more than 30 intentionally-set fires have hit the Coatesville community, just west of Philadelphia, the Philadelphia Inquirer reported online.

"Someone had pulled the trash can up to our back door and set it afire," one woman told CNN.

Dozens of families have been made homeless, while others have fled the area in fear, news reports said.

The investigation now includes local justice and fire officials as well as the Pennsylvania state police, the Federal Bureau of Investigation and the federal Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF).

"These fires share a commonality with the fires already under investigation, but at this point we will not say that they are directly linked to the arsonist or arsonists in Coatesville," ATF agent John Hageman was quoted as saying. (dpa)