PULLMAN - A pre-dawn fire heavily damaged a Planned Parenthood clinic in the college town of Pullman, Washington and a regional terrorism task force is working to determine whether it was arson.

The cause of the fire is not yet known, but FBI Special Agent Frank Harrill said federal agencies are involved because of the history of anti-abortion activists targeting health care providers offering abortion services.

Planned Parenthood spokeswoman Tanya Riordan told The Spokesman-Review newspaper that the clinic could be closed for a month or more due to the fire, which broke out at about 3:30 a.m. Friday.

Riordan said Planned Parenthood will look for a temporary office in Pullman so it can resume services as quickly as possible.

Pullman is home to Washington State University.