A black SUV was seen circling the Iowa neighborhood where Mollie Tibbetts was staying on the night she vanished, a neighbor revealed to Fox News on Sunday, in what could be a new clue to the college student's disappearance.

The driver went very slowly around the neighborhood the night of July 18, according to a young woman who lives a block away from the home of Tibbetts' boyfriend, Dalton Jack.

MOLLIE TIBBETS, UNIVERSITY OF IOWA STUDENT, MISSING: A TIMELINE OF EVENTS

Between 11:30 p.m. and 1 a.m., the woman said she observed the suspicious vehicle. She told Fox News that she reported it to the FBI when she was questioned. Investigators so far have not commented on it.

Tibbetts was last seen on July 18. The missing University of Iowa sophomore was last seen jogging in the area, where she was dog-sitting at her boyfriend's home.

Also on Sunday, an FBI agent questioned the owner of a nearby farm for the third time in connection with Tibbetts' disappearance, although it's unclear why. The agent questioned Wayne Cheney around 5:30 p.m. local time for roughly five to 10 minutes.

Cheney has told Fox News he was not involved in the 20-year-old's disappearance. The farmer has not been charged in Tibbetts' case.

He said he had never seen Tibbetts before, because he didn't venture into the Brooklyn area, which is several miles from his home. He added he'd allow the FBI to search his entire property and expressed confidence investigators wouldn't find anything.

The FBI last week searched his home and some of his property, and looked through his cellphone, the farmer said. He claimed that law enforcement asked him on Thursday to take a polygraph test but he refused to do so.

Authorities on Sunday said they've been following up on "hundreds" of leads in the case. Also Sunday, police said the body of a 20-something woman turned up in Lee County, but said the body was not Tibbetts.

The reward for Tibbetts' safe return jumped to $260,000 as of Sunday. Crime Stoppers of Central Iowa said the missing student's family hopes the reward money will lead to her return.

Fox News' Nicole Darrah, Madeleine Rivera and The Associated Press contributed to this report.