Cambodian police have said they fear missing British backpacker Amelia Bambridge has drowned.
Amelia Bambridge, from Worthing in West Sussex, was last seen on the island of Koh Rong a week ago.
Members of Ms Bambridge's family have travelled to the island to join in the search for the 21-year-old.
Major General Chuon Narin, police chief for Preah Sihanouk province, said searches would continue until she is found.
Ms Bambridge was reported missing after she failed to check out of her hotel on time.
Staff at Police Beach, a private venue on the island, found her purple rucksack with her purse, phone and bank cards inside the following morning.
Family and friends have attended a vigil at St Michael's Catholic Church in Worthing.
Father Christopher Ingel said her disappearance was the "most unimaginable thing" for her family, who had requested the vigil in order to "pray for her safe return and safety".
Major General Narin said searches of Koh Rong island and in the Gulf of Thailand failed to provide any information about her disappearance, but land and sea searches are due to continue.
About 150 volunteers including divers, navy personnel and visitors as well as Cambodian police officers are involved in searches.
Six men who work at restaurants, hotels and guesthouses on the island were questioned and released without charge on Tuesday.
Officials said the men were brought into custody because of complaints by Western tourists that they had acted badly towards visiting women.
On Wednesday, Ms Bambridge's family criticised the Foreign Office for a lack of support.
Members of staff from the Foreign and Commonwealth Office have been on Koh Rong island for a number of days.
A spokesman said: "Amelia's family have our deepest sympathies at this very difficult time.
"Our staff have been providing in-person assistance to them on Koh Rong island, and maintaining close contact with the Cambodian authorities searching for Amelia."