The family of a Briton missing in the Malaysian jungle have thanked those involved in the "fantastic" international search mission.
Backpacker Gareth Huntley, who is on a sabbatical from his job in the City, has not been seen since he went on a trek to visit a waterfall in Tioman Island, off the south eastern coast of the country's mainland, on Tuesday morning.
He told friends at the headquarters of a nearby charity project where he was volunteering that he would return by 2pm the same day but failed to come back.
The British Government has stepped up attempts to find the 34-year-old, who is originally from the Leeds-Bradford border, while Defence Secretary Philip Hammond has been assured that "all available search assets" are being used to find the trained accountant.
Mr Huntley's younger brother, Mark, said the family were keeping positive as a result of efforts to find him.
He said: "We want to personally thank David Cameron and Philip Hammond for their reassurances. It is a very big positive for us.
"We are, of course, very grateful to the Malaysian people and the authorities for their work too. Everyone has been fantastic.
"We are told that local people went out to look for Gareth as soon as he was first described as missing - so without them there would not be a search mission.
"What we need now is for that work to continue and to find my brother."
Mr Huntley's girlfriend Kit Natariga has now arrived on the island, while his mother, Janet Southwell, has arrived in Singapore from England and will head to the island at first light.
Ms Natariga said efforts to find Mr Huntley were a tonic to the anxiety, but admitted time to find him was "running out".
She told Sky News: "It's really tough coming onto the island, we're in a bit of a helpless state.
"We cannot give up... time is running out."
She said her boyfriend was an experienced backpacker and adventurer who would take utmost care in ensuring he was prepared for excursions.
An FCO spokesman said: "The Defence Secretary, who is in Malaysia, has spoken to the Malaysian Defence Minister this morning to confirm that all available search assets are used to find Gareth Huntley.
"He was assured that the Malaysian authorities would do all they could to locate him and had already deployed significant assets including dogs, boats and a helicopter.
"The Government will continue to work with the Malaysian authorities to ensure there is a comprehensive search."
Yesterday Mr Huntley's mother said "real help" was needed to find her son, from Hackney in east London.
In a direct plea to Mr Cameron, she said: "As a father, you know that we'd do anything for our children and so I'm humbly asking that you make one phone call to help my missing son, Gareth.
"Please do the right thing Prime Minister and make one phone call to the Malaysian leader to insist that they deploy real help to find Gareth before time runs out. He is out there in the jungle and he needs help.
"We've been hugely heartened by the public's fantastic support so far but we urgently need firm action from the Government - not standard press assurances of 'working with authorities'. We need boots on the ground, search teams and dogs so that we can bring our son back alive.
"As our Prime Minister I write to you but as a mother too, I hope you'll help me."
Mr Huntley's close friend, Kyle Neo Kai Fu, who is on Tioman Island, initially said the efforts to find the man were "laughable" and "sickening".
However, Mr Huntley's family have since reacted positively to British involvement.
Speaking following the meeting with Malaysian defence minister Hishammuddin Hussein - currently also investigating the disappearance of flight MH370 - Mr Hammond said: "I raised the ongoing search on Tioman Island with the Malaysian government to check they have all the resources they require.
"They assure me that they do and that they are doing everything they can to find Gareth. We will continue to keep in regular contact with the Malaysian civil authorities leading the search."