Wichita ? A suspicious letter found in a library drop box last weekend is being treated as a “possible communication” from the BTK serial killer, Wichita police said Thursday.

Lt. Ken Landwehr said the letter has been turned over to the FBI for authentication. No information has been released about the contents of the letter, which a library employee found in the drop box at the city’s main library on Saturday.

The BTK killer has claimed responsibility for eight deaths in Wichita, the first in 1974. The letters “BTK” stand for “bind, torture, kill.”

Attention has refocused on the case since March, when The Wichita Eagle received a letter containing information about an unsolved 1986 killing. The letter contained a copy of the victim’s driver’s license and photos of her taken after she was slain.

It was the first communication from the killer known as BTK Strangler in more than two decades, and police said it linked the serial killer to an eighth slaying. Seven people were slain in the 1970s, with BTK taking credit for those deaths in letters to the newspaper and a television station.

In May, Wichita television station KAKE received a letter, and investigators have said they believe that letter is also from BTK. Since BTK resurfaced, police have received more than 2,200 tips about the case.

Landwehr said Wichita residents should continue to be aware of crime prevention techniques. He said the letter sent to KAKE indicated the writer had used false identification in the past to gain entry to homes.

“We don’t want any of our citizens to fall prey to this ruse,” Landwehr said.