Newly unsealed documents show investigators looked closely at four other potential suspects before they made an arrest.
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TIMELINE: Mollie Tibbetts' disappearance
That includes a neighbor seen washing his SUV hours after Tibbetts vanished, a Nebraska man who ditched his vehicle in Iowa, an acquaintance of Tibbetts who "wiped" his cellphone data, and a farmer with a history of stalking women.
After facing police interviews and vehicle and cellphone searches, all were eliminated as suspects.
The suspect ultimately charged in Tibbetts' death, Cristhian Bahena-Rivera, did not come on their radar until shortly before he allegedly led them to her body in a cornfield in August.
RELATED: What we know about the suspect charged in Mollie Tibbetts' death
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Investigators say Rivera, 24, followed Tibbetts in a car and then on foot as she was out for an evening run, kidnapped her after a struggle and stabbed her to death.
Rivera was identified as a suspect after officers found surveillance footage showing a Chevy Malibu that they later linked to him. Rivera, who is scheduled to stand trial, is a Mexican national who was allegedly in the U.S. illegally .
He is due to go to trial in April.
Get the latest updates on the Mollie Tibbetts case here.
The Associated Press contributed to this article.