( CNN ) -- A California woman missing for nearly a year and believed to be dead may still be alive and living in the Las Vegas , Nevada , area , detectives from Los Angeles said Thursday . Investigators have spent about six weeks checking out a high-school classmate 's report that he saw Mitrice Richardson at a hotel casino , and are `` unable to show that it is not a good lead , '' Los Angeles police Capt . Kevin McClure said . And detectives have talked to several witnesses since then who believe seen her in the area , he said . `` It is not a verified sighting of her here , but we feel good enough to come up here and spend a good deal of time to get the information out to the community that we believe she might be here , '' McClure told reporters at a news conference in Las Vegas . But Richardson 's mother , who is suing the Los Angeles County Sheriff 's department over her daughter 's disappearance , cast doubt on the report . Latice Sutton told HLN 's `` Issues with Jane Velez-Mitchell '' that the man who reported the sighting has n't seen her daughter for a decade . Richardson , who would be 25 now , is a former beauty pageant contestant who was last seen leaving a Los Angeles County sheriff 's station in Malibu in the early morning hours of September 17 , 2009 . She had been arrested the previous evening at an upscale restaurant for allegedly not paying for her meal , and patrons at the restaurant said Mitrice exhibited strange behavior . Her family has said the college honors graduate suffered from mental health issues and should have been kept at the sheriff 's station until a relative arrived to pick her up . Investigators are now asking the public in and around Las Vegas to report any possible sightings , and urged Richardson herself to come forward . `` She 's not in any type of trouble , '' said Capt . Dave Smith , of the Los Angeles County Sheriff 's Department . `` She 's not subject to any type of arrest We would like her to approach her family , approach us , and please let us know that she 's OK. '' A high-school classmate now living in Las Vegas reported seeing Richardson at the Rio Hotel and Casino in early June , sparking the new effort by detectives to check out his report . `` He walked up and said , 'Hi , Matrice , '' Smith said . `` She basically looked at him with kind of a shocked look and left the location . '' The casino 's security cameras did n't have video of the incident that was of a high enough quality . But since then , investigators have talked to more than 70 people who say they have seen her , said William McSweeney , chief of the Los Angeles County detective division . Those accounts were `` based on a photograph and some passage of time , in most instances , '' McSweeney said . `` But that volume causes us to beleive we 're on the right track . '' But Sutton told HLN on Thursday , `` I do not believe it was her . '' She said hundreds of similar reports in Los Angeles have failed to pan out , while the man who reported seeing her in the casino had n't seen her daughter since high school . And she questioned why police considered that report believable after dismissing an earlier report by Michael Richardson , the missing woman 's father , that he had spotted his daughter in Las Vegas . `` Someone who has n't seen Mitrice in 10 years , they consider him now more credible than the biological father ? Sutton asked . `` I do not believe this is Mitrice . Mitrice was last seen at the sheriff 's department . '' Last month , Sutton sued Los Angeles County and several sheriff 's officials for wrongful death and negligence in her daughter 's disappearance , according to court documents . Sutton argued that the sheriff 's department failure to administer psychiatric or medical evaluations and the fact that Richardson was released `` alone in an unfamiliar area without money , a cellular phone or means of transportation amounts to negligence . '' The lawsuit seeks unspecified monetary damages . Steve Whitmore , a spokesman for the sheriff 's department , told CNN in September that the decision to release Richardson was made because `` she was not intoxicated , she did n't exhibit any mental issues , so when we were done running her fingerprints and criminal history , then we are obligated by law to release her from custody . '' He also has said that a female jailer `` offered to her to stay the night . She could have stayed , but she wanted to leave . '' Police have not discounted the possibility that Richardson may not want to be found , but her family believes that would be `` out of her character '' McClure said . `` We could find that out , but we 'll never know that until we actually talk to Mitrice , '' he said . CNN 's Gabriel Falcon contributed to this report .
NEW : Mom discounts missing woman 's sighting in Las Vegas . Mitrice Richardson has been missing for nearly a year . A high-school classmate says he spotted her in a casino in June . Police say they have more than 70 other possible sightings .