One teenager who had been missing for two months was "angry, upset and crying" the day he was last seen.
Leah Croucher, 19, disappeared around 8:15 GMT on February 15 when he went to work at Buzzacott Lane in Furzton, Milton Keynes.
The Thames Valley police said three people reported possible sightings of Ms. Croucher at Furzton Lake between 09:30 and 11:15 that day.
All three said they think they saw the woman on her phone.
The first witness reported that between 9:30 and 10:00, a woman typed on her cell phone at the lake.
Two other witnesses, who walked together, described a woman who was obviously angry and angry and cried between 10:00 and 10:15.
About 20 minutes later, they saw the female again, saying that she was in a calmer state and possibly talking to someone on her cellphone.
Ch Insp. Neil Kentish said: "We are trying hard to establish the identity of the person described to us by the three witnesses.
"Even if that person was not Lea, we'd still like to talk to them so we can remove the sightings from our investigation."
Mr. Kentish described the investigation of the disappearance of Leah as "extensive." Officials visited 4,000 homes and spoke to 100 potential witnesses.
The squad collaborated with the main punishment unit, family officials, search teams, the mounted department, police dogs, ship specialists and the national police service.
Leah's parents, Claire and John Croucher, said in a statement: "It has now been 62 long and heartbreaking days since our beautiful, wonderful daughter Leah was blown up.
"When Leah was reported missing for the first time, we honestly believed that she would be home soon.
"But that did not happen and as each succeeding day begins, we are in desperation that another night has come and gone and we have not received a call or visit, which means that Leah is still missing."