The Iowa pig farm owner who has been questioned multiple times about the disappearance of Mollie Tibbetts declined to take a lie detector test about the case, according to former Detective Ted Williams.

Williams, a Fox News contributor, said Monday that he spoke to Wayne Cheney and asked him why he wouldn't take the test.

"He said 'No, no' and he continued to say no," Williams said on "Fox & Friends."

When asked by Williams if he did in fact want to assist in the investigation, Cheney said that he did, but still rejected the notion of a lie detector test.

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Tibbetts has been missing for more than two weeks after being last seen on July 18 in Brooklyn, Iowa.

Cheney had told Fox News that FBI officials asked to search his home July 26 without a warrant.

Investigators returned to Cheney's home last Friday, and he also said he had been told they were to return Sunday as well.

Authorities have also ruled out the possibility that a woman's body found more than 100 miles from where Tibbetts was last seen was actually her.

"This is very scary," Williams said. "One of the big questions out there is, is there a serial killer? Why are young people out there dying?"

A neighbor also told Fox News that a black SUV suspiciously circled the neighborhood where Tibbetts had been staying the night she disappeared.

Watch the segment from "Fox & Friends" above.

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