Melissa Mac, who had not been to school at Northampton Academy since July, went missing on Friday, February 15, in Northampton town centre.

The 15-year-old has not been in touch with her family since but there have been sightings of Melissa in Wellingborough and Milton Keynes.

Thao Mac, who believed her daughter was still in Northamptonshire, said: "What can we say? It's been difficult but we just have to try and stay positive.

"Melissa has two sisters and they miss her but they're a lot younger than her. We just try and do our best."

Police investigating the case believe Melissa went missing on her own terms but are concerned for her because of her age.

Detective Inspector Julia Potts said: "Melissa's 16th birthday is coming up and we would again appeal for her to get in touch with us or her family.

"We are hoping that she will use the occasion as an opportunity to speak to us.

"We have regular contact with her family and they are devastated. They just want Melissa to pick up the telephone and tell them that she's OK."

Melissa is of Chinese/Vietnamese origin and is about 5ft 4in with straight black hair.

Anyone who knows where Melissa is, or Melissa herself, can contact Northamptonshire police on 08453 700700.