Six men are being questioned by police in Cambodia investigating the disappearance of British backpacker Amelia Bambridge.
The 21-year-old, from Worthing, West Sussex, was last seen at a beach party on the island of Koh Rong on Wednesday night.
Among those detained by police are men who worked at bars on the tourist island, a senior Cambodia police officer said.
Ms Bambridge's parents and brother have flown to the island to assist with the search and her father said he feared she had been abducted.
Around 200 soldiers and police using drones and divers have joined the widescale search operation.
Read more of today's top stories
A purple rucksack containing her watch and mobile phone has been recovered as part of the search on a rock near the water's edge.
Photos of Ms Bambridge had been posted online until 3:23am but her whereabouts after this are unknown.
Nuon Bunthol, the Koh Rong town governor, said: "We are very worried that's why we are using all forces to search for her."
Her brother, Harry, wrote an appeal on Facebook to share as much as possible about her sister to put more pressure on the island to find her.
He said the language barrier was causing problems and he described how "there is nothing making sense and something's not quite right".
She set off on her trip on September 27 and flew first to Vietnam, her family said.
Amelia had been staying at the Nest Beach Club hostel on Koh Rong.
When she failed to checkout of the property, her family were alerted.
On the night of her disappearance, she was with friends she met at the hostel and they went to Police Beach, named after its location close to a disused police station.
