(Image Credit: Lafayette Police Department/AP Photo)

One of the vehicles, a white pickup truck, was immediately recognized by Tasha Patterson, a Lafayette woman who said she was approached two months ago by the vehicle while riding her bike and the driver, a middle-aged white man, offered her a ride and then asked her to have sex with him for money.

"He says he rides around town all the time trying to pick up pretty girls," Patterson told ABC News affiliate KATC, although it's unclear whether she accepted the ride.

Police are looking for the white, newer-model pickup truck with tinted windows, in addition to a four-door sedan and a second four-door white Chevy truck seen on the surveillance video.

Police released details of the surveillance video as they sought to uncover more details about how Shunick, 22, disappeared while bicycling home from a friend's house early in the morning May 19. Shunick, a senior anthropology major at the University of Louisiana, was an avid bicyclist, according to family members.

Police located Shunick's bike Sunday - a black and gold Schwinn - underneath a bridge along the Atchafalaya River, more than 27 miles from where she left her friend's home. They have searched the area with all-terrain vehicles and boats for any signs of Shunick.

"We've expanded as wide as what we feel comfortable that we don't miss anything," Officer Paul Mouton of the Lafayette police department said. "It is quite a large area down beneath the bridge."

Police said the search will continue today for Shunick.