Police have released pictures of missing teenager Megan Stammers and her teacher Jeremy Forrest taken on board a ferry to France.
The CCTV images show the couple walking hand in hand on the Dover to Calais vessel at 9.30pm last Thursday. It comes after it emerged their relationship had been under investigation before they ran away together.
Chief Inspector Jason Tingley, from Sussex Police, said: "We are releasing this photo to show Megan and Jeremy's appearance at the time they travelled to France as we believe it will improve the public's ability to recognise the pair together.
"Although they entered France, it is possible that they are elsewhere now. Therefore our objectives are to identify where they are and for them to contact us, so we can bring Megan home safely."
The parents of the 15-year-old have made an emotional appeal for her to get in contact with them.
It has now emerged that concerns were expressed to another teacher about their relationship, following a school trip to Los Angeles in February.
A friend from Bishop Bell Church of England School in Eastbourne, East Sussex, said that another classmate had raised the issue after seeing the pair holding hands on the flight home.
The 15-year-old said: "I kind of knew it was gonna happen because of the way they were with each other and my friends were talking about it when they were on the LA trip.
"It was obvious it was gonna happen. They were always together... on the plane apparently they were holding hands."
An East Sussex County Council spokesman said: "Because the investigations are ongoing, we are not going to comment in detail, however the school and the county council had been addressing and investigating concerns that had been raised, in line with procedure, when this happened.
"That investigation will continue and we will decide what action to take."
The pair travelled on a ferry from Dover to Calais on Thursday evening and were due to come back to the UK on Sunday, but did not use their return tickets.
A text message, believed to be from the teenager, was sent to one of her friends saying she had arrived safely in France but did not come from her own phone, police revealed.
On Monday, Megan's parents urged the teenager to come home.
Her mother Danielle Wilson made a direct appeal to her daughter, saying: "Sweetheart, I don't care what you've done or why, I just want you home."
With her voice breaking, she also said: "Please darling, just do anything - text me, ring me, send me a message. I've sent you a message on Facebook, just do anything. The phone number hasn't changed at home, just ring, please sweetheart."
Describing her daughter as "so loving, so caring", Ms Wilson added: "You know that your adorable princess wants her adorable mermaid back."
Her father Martin Stammers described Megan as "just adorable". He added: "I just want you to come home safe and well."
Both parents said her disappearance was out of character.
"She is always in at 7pm, she is not one of these kids to roam the streets, she doesn't go out drinking or anything like that. She doesn't like the dark so she had never been out after dark," Ms Wilson said.
She added: "It is completely out of character, this is not her, she is not like this."
Megan's family have set up a website Megan Stammers Missing to raise awareness of her disappearance.
Appeals for information have also been posted on Facebook and Twitter. On social networking site ask.fm, Megan recently said she was "excited" about her future and that her motto in life was "You only live once".
In 2009, a teacher at Bishop Bell C of E School was jailed for seven years after grooming two pupils on social networking site Bebo.
Robert Healy, then aged 27, had sex three or four times with one teenage victim after taking her back to his father's house over a period of a fortnight.
Jailing him at Lewes Crown Court, Judge Charles Kemp said his "predatory" behaviour was a "grave breach of trust".
Police believe Megan had left the UK willingly and urged her and Mr Forrest to contact them.
Mr Tingley appealed for any members of the public who see the couple or Mr Forrest's black Ford Fiesta, registration GJ08 RJO, to contact police.
:: Anyone with information is asked to call Sussex Police on +44 1273 475 432 or text +44 7786 208 090.