Wichita ? Police say they are treating a recent letter sent to a Wichita television station as “possibly” coming from the BTK serial killer.

In a brief statement read Monday to reporters, police Lt. Ken Landwehr said the department was turning the letter over to the FBI, where analysis will work to determine the letter’s authenticity.

The letter was received by KAKE-TV last Wednesday. The station reported that the letter contained a puzzle and photocopies of employee identification cards for two men: a former Southwestern Bell worker and a former employee of the Wichita public school district.

Authorities believe the serial killer — known as BTK, for “Bind, Torture, Kill” — killed at least seven people between 1974 and 1978.

In March, BTK resurfaced when he sent a letter to The Wichita Eagle newspaper claiming responsibility for an eighth killing in 1986.

Police are again asking for help from the public based on information contained in the latest letter.

They want to talk to residents who recall a man seeking access to their home by presenting identification as an employee of a school or utility company between 1974 and 1986.

“Obviously, we are not interested in legitimate encounters,” Landwehr said. “We want to know about situations where a man attempted to get into your house under suspicious circumstances.”

BTK has a history of taunting police with letters to news organizations. Letters claiming responsibility for the slayings, which remain unsolved, were sent to The Wichita Eagle and KAKE-TV, the last coming in 1979 until the letter to the Eagle surfaced earlier this year.