Updated

The parents of missing 20-year-old Lauren Spierer are suing the three former college students who were the last men known to see their daughter alive, the family's attorney tells FoxNews.com.

Spierer, a sophomore at Indiana University from Greenburgh, N.Y., disappeared two years ago from downtown Bloomington after a night of partying with a group of friends and acquaintances.

Robert and Charlene Spierer claim in their civil lawsuit that their daughter's last known interaction with the men -- Corey Rossman, Mike Beth and Jay Rosenbaum -- resulted in her "disappearance, death or injury," according to attorney Jason Barclay.

The complaint says that the men's negligence led to her disappearance, which remains unsolved, according to police.

The lawsuit was filed last month in Monroe County, Ind. The complaint seeks a jury trial against the men, who are no longer students, and monetary damages.

"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."

Any parent in search of information about a missing child would use every resource available to them," he 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."

Click here to read the complaint.

Fox News interviewed the Spierers last month in an exclusive on-camera interview during which they expressed doubts the men were telling the truth about their daughter's last hours.Robert Spierer said he is not convinced Lauren ever left the men's apartment building, which was her last known stop that night.

Rossman, who claims he remembers little of what happened that night, was seen on surveillance video and by witnesses accompanying a visibly incapacitated Spierer as the two made their way from a popular bar to her apartment and then to his place over the course of a few hours.

According to investigators, Spierer, a fashion merchandising major, left her Smallwood Apartment complex with a friend, David Rohn, shortly after midnight. The two headed to Rosenbaum's apartment, where other students had gathered with ample amounts of alcohol.

Spierer then left with Rossman, whom she had met a week prior at the Indianapolis 500, and walked to Kilroy's Sports Bar at 1:46 a.m. Spierer, who was not of drinking age, entered the popular hangout, which has a sandy, outdoor beach-like area where students often walk barefoot. At 2:27 a.m., Spierer was seen on camera leaving the bar without her shoes and cell phone and heading, with Rossman, back to her apartment complex.

Upon reaching her floor at Smallwood, an altercation occurred between Rossman and another student, Zachary Oakes, according to the woman's family. Oakes, they said, punched Rossman to the floor. It’s not clear what precipitated the fight, but the Spierers say they were told Oakes and others ordered Rossman to bring the inebriated woman to her room – and that an exchange of angry words ensued.

Twelve minutes later, Rossman and Lauren left Smallwood and walked through an alleyway en route to Rossman’s apartment building. Law enforcement sources told FoxNews.com that Rossman was at one point seen carrying Spierer, who appeared unable to walk.

Rossman has said he lost all memory after being punched by Oakes – a claim Rob Spierer called "a story of convenience."

"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.

Many questions surround what happened next.

Mike Beth, Rossman’s roommate, was said to have helped him to his bed. Beth, who was working on a class assignment, then walked Spierer down the hallway to Rosenbaum’s apartment. Rosenbaum, who had two non-students staying with him that weekend, claims he tried to convince Spierer to sleep on his couch. After she refused, according to Rosenbaum, he watched from his balcony as Spierer – barefoot and without her cellphone – walked home alone in the dark. The walking distance between the two apartments took approximately six minutes, according to police.

"For her to recover in such a short period of time, call it an hour or more, doesn’t make sense to me," Rob Spierer said.

Rossman and Rosenbaum declined to comment when contacted repeatedly by Fox News. Beth could not be reached.

If Rosenbaum’s story holds true, Spierer was an ideal target for a predator looking to abduct a woman, according to former FBI agent Mike Harkins.

"Certainly she was a very vulnerable individual," Harkins said in an interview last month. "Her petite size, her condition she was in would have made an easy target for someone looking to commit that type of a crime."

Anyone with information on the case is urged to call the Bloomington Police Department 24-hour tipline at 812-339-4477 or contact them by email at policetips@bloomington.in.gov.