Wichita ? The BTK serial killer has sent investigators at least three packages containing jewelry that may have been taken from his victims, police said Thursday.

Wichita police Lt. Ken Landwehr, commander of the BTK task force, told reporters that investigators were trying to determine whether any of the jewelry belonged to the victims.

“I still contend that this is our most challenging case, but I am very pleased with the ongoing dialogue through these letters,” Landwehr said.

The BTK killer — the initials of the killer’s self-coined nickname stand for “Bind, Torture, Kill” — has been linked to eight unsolved killings, committed between 1974 and 1986. He resurfaced in March by sending letters to media and police.

Landwehr said Thursday that the FBI’s behavior analysis unit had confirmed that two letters were authentic communications from BTK, including a letter dropped in a United Parcel Service Inc. box in October 2004.

“This communication contained information about BTK that was subsequently released to the public on Nov. 30, 2004,” Landwehr said. “The FBI can confirm that it is a BTK communication but cannot confirm the accuracy of the information he wrote about himself in the letter.

The other confirmed communication was a package found in December by a Wichita resident in Murdock Park. That package contained the driver’s license of Nancy Fox, who was killed on Dec. 8, 1977.

The most recent communications that have included jewelry were a cereal box found in a rural area northwest of Wichita in late January, a package found a few days later that police have identified only as communication number seven, and a package sent Wednesday to KSAS-TV in Wichita.

All have been sent to the FBI for analysis and authentication, Landwehr said.

The padded manila envelope received Wednesday at KSAS contained a piece of jewelry, a letter and another unidentified item, said Don North, the news director at KWCH-TV, which produces the KSAS newscast. He declined to further identify the items at the request of police.

BTK has communicated primarily with Wichita’s KAKE-TV, but the letter included in Wednesday’s package indicated the killer wanted to spread his communications to other stations.

“KAKE is a good station, but I feel they are starting to be single (sic) out, because of me, and causing problems among the people. Let’s help the news media and WPD (Wichita Police Department) by using this package as a start,” the letter read.

The letter’s return address said “PJ Fox” and listed KSAS’s address.

“It was an unusual letter, kind of weird. It wasn’t real long at all,” North said. “The way it reads I don’t know if the guy felt sorry for KAKE or felt sorry for the other TV stations.”