Washington, D.C., police believe the car Rep. Gary Condit was in when he discarded a watch box belonged to one of his senior aides, who was driving the car, law enforcement sources have told Fox News.

Sources close to the investigation into the disappearance of federal intern Chandra Levy say they have searched two cars belonging to the congressman's staffers in recent weeks, and that they can't rule out that Condit's aides may be called by the U.S. attorney's office at some point.

Police, who have already interviewed Condit, D-Calif., three times about the missing woman, want to talk to him again, this time about the watch box the married 53-year-old reportedly threw out in a suburban park hours before police searched his apartment on July 10.

"We want to follow up to find out what there is to it," Gainer said.

But police do not believe the watch box has any relation to Levy's disappearance, officials said.

Sources have told Fox News that the watch the box held was a Tag Heuer given to Condit by a 29-year-old California woman who worked for him in an administrative position in 1994.

"If the police or FBI have anything new they want to discuss, we're happy to cooperate," said Condit's spokeswoman, Marina Ein.

Ein declined comment on a possible time or place for a fourth meeting, which police officials have said could happen this week.

Investigators have become frustrated with the silence of some of Levy's neighbors, who still have not responded to appeals for help in finding the missing woman.

Executive Assistant Police Chief Terrance Gainer said there are still "far too many people, more than a handful," in Levy's apartment building who have yet to be interviewed about the 24-year-old graduate student's disappearance.

Levy's close neighbors could supply important information about her actions and visitors in the days before she vanished, Gainer said, adding that his department does not consider anyone in the building a suspect.

"It's part of the irritating thing about this. We've been to the building a half-dozen times, we've knocked on doors three or four times and now we've slipped notices under the door," Gainer said in an interview. "But this is America, and absent acting like jack-booted thugs, we can't force them to talk to us."

Meanwhile, Levy's parents on Tuesday released new home videos of their daughter taken two years ago. Chandra can be heard speaking on the videos, answering questions about school. Susan and Robert Levy allowed the videos to be broadcast in the hope that they might help lead to information about their daughter's whereabouts.

Also, a representative from the Carole Sund Memorial Foundation, which helps locate missing persons, told ABC's Good Morning America Tuesday morning that the reward for locating Levy has reached $200,000.

Condit, who has admitted having had an affair with Levy, who was from his congressional district, donated part of the reward money, the representative said.

Levy, of Modesto, Calif., was last seen April 30 as she canceled her membership at a Washington gym, shortly after her internship at the Federal Bureau of Prisons was abruptly cut short because she revealed that her graduate studies at the University of Southern California had technically ended.

Computer records indicate that she used her home computer to surf the World Wide Web and e-mail friends and her parents from about 9 a.m. to 1 p.m. the following day, May 1. Her wallet, credit cards and identification were found in her apartment, along with a set of partially packed bags. Levy's parents have said they expected her back in California by May 11.

The police have said they would like Condit to submit to a supervised lie-detector test, and have rejected the congressman's self-arranged polygraph test, which his attorney said he passed, as meaningless.

Investigators want to enlist Condit's help in developing a profile of Levy, a former intern at the U.S. Bureau of Prisons, as a possible crime victim, Gainer said.

An FBI behavioral psychologist probably would sit in on the interview and attempt to elicit from Condit some information about where Levy may have gone or who may have targeted her, assuming she was harmed, Gainer said. 

Police have said they do not consider Condit a suspect in Levy's disappearance, which they are treating as a missing-persons case, not a crime.

Police recruits will once again be searching local parks for clues Tuesday, said departmental spokesman Joe Gentile, concentrating their activities two areas in the Northeast and Northwest sections of the city.

Fox News' Rita Cosby and The Associated Press contributed to this report