The parents of Lauren Spierer, a missing 20-year-old college student, filed a civil lawsuit against the three men last seen with her before disappearing, the Associated Press reported.

Spierer was a sophomore at Indiana University when she went missing two years ago; her case is still unsolved, police said. According to reports, Corey Rossman, Mike Beth and Jay Rosenbaum were the last to see Spierer alive during a night of partying in downtown Bloomington.

Robert and Charlene Spierer's complaint said the three men were responsible for their daughter's "disappearance, death or injury," according to attorney Jason Barclay. The suit also said negligence led to the disappearance.

"Rob and Charlene Spierer authorized the filing of this lawsuit with great reluctance and only after we counseled them that they would lose certain legal rights if not exercised by the two-year anniversary of Lauren's disappearance," Barclay said in a statement. "We hope no one will misinterpret this action."

Spierer's parents have been the most diligent proponents of the search all along, even when the case turned cold.

"Any parent in search of information about a missing child would use every resource available to them," Barclay said. "Therefore, we intend to use the rights afforded by the civil justice system to obtain answers to questions that have gone unanswered for too long. We fully expect that those with relevant information will cooperate with this process."

In an interview last month with Fox News, the two parents said they did not believe the three men were being completely honest about the night in question. Robert said he was not convinced his daughter ever left the last confirmed spot where she was seen: the men's apartment building.

According to investigators, Spierer, who was underage at the time, was confirmed to have attended a downtown sports bar with a beach area where attendees frequently walked through barefoot. Spierer was seen on camera leaving the bar with Rossman and without her shoes or cell phone.

The two were en route to Spierer's apartment when Rossman got into an altercation with another student named Zachary Oakes. Robert and Charlene believe Oakes told Rossman to return Spierer, who was visibly inebriated, back to her room. The fought and Oakes punched Rossman to the ground.

Rossman said he lost most of his recollection at that time, but the two reportedly were seen heading to the men's apartment with Rossman carrying Spierer because she apparently was unable to walk.

Robert believes Rossman's loss of memory is too convenient.

"How they both got back to Corey's apartment had to be a result of the initiative of Corey and certainly not Lauren, so I don't know how bad a shape he could have been in because he was able to get both he and Lauren back to his apartment after he got hit at Smallwood," Spierer said.

Beth said he helped Rossman into his bed and then brought Spierer to Rosenbaum's room. Rosenbaum tried to convince her to sleep on his couch, but she refused and decided to make the six-minute walk to her apartment. Rosenbaum said he recalls watching her from his balcony walk barefoot into the dark.

Click here to visit the family of Lauren Spierer's official Facebook page for updates and information.