A 30-year-old man believed to have run away to France with a 15-year-old schoolgirl is one of her teachers, sources said tonight.
Police have appealed to Jeremy Forrest or Megan Stammers to make contact after eloping across the English Channel.
It is believed that Forrest is a maths teacher at the same school that Megan attends, Bishop Bell C of E School in Eastbourne, East Sussex.
There have been no reported sightings or contact with the pair since they vanished, and police were tonight pursuing "critical lines of inquiry".
The alarm was raised at mid-day on Friday after Megan failed to turn up for school.
Nine hours later she crossed from Dover to Calais, sparking an appeal to trace her.
Police have said they do not believe Megan is at risk but they are in contact with the French authorities in an effort to reunite her with relatives.
Her father, Martin Stammers, said yesterday: "We just want Megan to make contact with us. We are worried and miss her terribly. Please get in touch, Megan."
Chief Inspector Jason Tingley said they were at a "critical stage of the investigation" and officers were grateful for the support of Megan's family and friends.
Appeals for information about her whereabouts have been posted on Facebook and Twitter, including from her worried father.
He tweeted: "Have to remain strong for Meg's, can't dwell in the misery of 'what ifs' - we love you sweetheart, doing all we can #findmeganstammers."
One poster on Facebook wrote: "Hope she's back home with her family soon."
Officers have appealed for information about the whereabouts of a black Ford Fiesta, registration GJ08 RJO, driven by Forrest, from Ringmer, near Lewes.
Mr Tingley, the Lewes district commander, said: "We are investigating several lines of inquiry and are grateful for the support and cooperation from Megan's family and friends."
He added: "Her family are incredibly worried and want her to come home."
Anyone with information is asked to call Sussex Police on 101.