PORTLAND, Ore. - The FBI offered a $5,000 reward yesterday for help tracking down whoever mailed dozens of threatening letters - including some containing a potentially harmful insecticide - complaining about TV coverage of college cheerleaders.

The letters were sent to national networks and their local affiliates, as well as people in states throughout the West and Midwest, according to the FBI office in Portland. Recipients also included people associated with university athletic departments in Ohio, Michigan and Arizona.

The initial batch of letters was postmarked in Portland and delivered in September 2004. Subsequent batches of letters were delivered between November 2006 and February, mostly with postmarks from Seattle, but some also were sent from Chicago, the FBI said.

The letters claim camera crews spent too much time on closeups of cheerleaders. One letter also complained about coverage of WNBA players.

Some of the letters contained various powdery substances, which the FBI laboratory determined was an insecticide. An FBI spokeswoman declined to identify the chemical. No injuries have been reported, authorities said.

The FBI released excerpts of two letters in the hope of identifying who sent them.

In a letter sent in September 2004, the author objects to the timing and angles of the shots captured by camera crews during sports events.

"We have asked nicely for them to respect us and all women, yet they refuse. They exploit innocent people, so we will too. When they start respecting us, we stop mailing these out," the letter reads.

The author of a letter sent in December 2006 complains that networks unfairly favor more modestly dressed cheerleading squads.

"For the last 6 years, Ohio State cheerleaders have received more TV time than any other Division I-A cheer squad on ESPN, because they wear long sleeved red/white outfits. If they wore sleeveless outfits, they would not get ANY TV time. So, we are fed up with this constant exploitation," the author wrote. *