Fox News said Tuesday one of Sjodin's roommates identified the shoe as matching one that Sjodin owned. Grand Forks County Sheriff Dan Hill said divers were searching the frigid Red Lake River for any other signs of the missing woman.
Sjodin disappeared from a Grand Forks mall Nov. 22. A suspect named Alfonso Rodriguez has been arrested. Bloodstains and a knife were reportedly found in Rodriguez's car.
The Grand Forks Herald said the knife was discovered in a wheel well soaking in a cleaning solution.
The governors of North Dakota and Minnesota planned to hold a news conference later Tuesday to announce the deployment of National Guard troops to help look for Sjodin.