"They're treating it as a suspicious circumstance and we're in contact with them," Salt Lake City Police spokesman Capt. Scott Atkinson said.
The vehicle was described as a light blue or gray Chevrolet Astro van with Pennsylvania license plate number ECJ 1368. It was spotted at a Texaco service station on Thursday morning in Lincoln, Nebraska about 880 miles from Salt Lake City.
"She was about 14 years of age. She was distraught and when a second person had looked into the van, they had pulled the young girl down," Elizabeth's uncle David Smart said, describing the witness reports in Nebraska.
"They said they saw a pair of arms come from the back and pull her into the back, but nobody got a look at that person," Lincoln police Sgt. Larry Barksdale said Monday.
Barksdale said police know who owns the van, but don't know the vehicle's current whereabouts. He said the driver and a male passenger took their time buying gas and cigarettes, and were not acting suspiciously.
Authorities said they have not connected the sighting to Smart, 14, nor have Salt Lake City police.
"We don't have a whole lot of information," Salt Lake City police Sgt. Fred Louis said Monday. "It's not clear what they have."
Salt Lake City Police continued to focus on handyman Richard Ricci, 48, a career criminal who has admitted stealing items from the Smart home when he was doing odd jobs there last year.
Ricci had been scheduled to appear in court on Wednesday, but the hearing has been delayed until July 31 because his attorney had a scheduling problem.
Ricci has maintained he had nothing to do with the kidnapping and his wife has said he was with her in the early hours of June 5 when Elizabeth was kidnapped at gunpoint from the family's million-dollar Salt Lake City home. Her 9-year-old sister Mary Katherine was the only witness.
Ricci was arrested on June 14 on an unrelated parole violation after police said they became suspicious of his alibi for the time of the kidnapping.
Smart family members have urged him to disclose to police anything he may know about the kidnapping.
A mechanic told police Ricci picked up his white Jeep Cherokee on May 30, returned it June 8, three days after the kidnapping. Police want to know who picked Ricci up at the mechanic's when he dropped off the car.
"We're still looking for the guy who was across the street," Atkinson said.
The Smart family has continued organizing search efforts for the girl whose picture has been put on billboards and the Internet.