Dru Sjodin, 22, a University of North Dakota student from Pequot Lakes, Minn., vanished Nov. 22 after leaving her job at the Victoria's Secret at Columbia Mall in Grand Forks.
"Dru, we will find you," Grand Forks Police Chief John Packett said at a briefing Tuesday. "With the arrest of Alfonso Rodriguez Jr. last night, this investigation has only reached the 50-yard line. As additional charges and information comes available, we will not be satisfied or comforted until such time as we find Dru."
Rodriguez, 50, was arrested Monday in Crookston, Minn., about 30 miles from Grand Forks, where he lives, police said. He had been expected to appear in court Tuesday, but officials said the appearance would be delayed until Wednesday morning.
Authorities declined to say Tuesday whether Rodriguez was cooperating.
"Our entire focus on this is in finding Dru," Grand Forks County state's attorney Peter Welte said. "This is by no means the end. This is a marathon and not a sprint."
Sjodin's father and brother spoke directly to their sister.
"Honey, we will find you," her father, Allan, said. And her brother, Sven, added: "I know we are just around the corner from you right now. We love you. Keep strong."
Rodriguez has a history of sexual contact and attempted kidnapping with adult women, and has used a weapon in at least one assault, according to a Minnesota Department of Corrections summary of his criminal history posted on the agency's Web site.
His past offenses require that Rodriguez be registered as a predatory offender, the department said.
Police and university officials told Sjodin's sorority sisters about the arrest and that the suspect is a sex offender, reports Bridget Bornstein of CBS station WCCO.
"That scares me a little bit," said Randi Canady. "We just hope that he didn't do anything to harm our friend ... The first thing that kind of popped into our heads was, he is a level three sex offender."
The case had drawn more than 1,300 volunteers who have searched without success. In addition, about 30 FBI agents, along with investigators from 20 different agencies in three states and the Canadian province of Manitoba, were working on the case. A $140,000 reward was offered.
Law enforcement agencies also have conducted smaller searches based on a few of the nearly 900 leads authorities have received in the disappearance of Sjodin, Grand Forks police Sgt. Michael Hedlund said.
Soon after Sjodin disappeared, her boyfriend, Chris Lang, called the student's roommate, saying he had received two calls. The first was cut off and Lang heard Sjodin say, "Oh, my God," before the phone went dead. During a second call a few hours later, there was only the sound of static and numbers being pressed.
However, Bornstein reports a cellular tower continued to pick up the signal for another 24 hours, which is why searchers have concentrated on the area within the tower's range.
Neighbors said Rodriguez lived with his mother, Dolores. No one answered the phone at the home Monday night.
Sonja Thygeson, who lives about four houses down from Rodriguez and his mother, said she's never seen him do anything wrong, but took precautions anyway.
"I'm a widow and I'm older, and I was scared, so I had my son-in-law come over and install a motion light after he (Rodriguez) moved in," Thygeson said.
Another neighbor, Milton Stave, said "there were a lot of frightened people around" when Rodriguez returned to the community.