The body of British backpacker Amelia Bambridge has been found at sea more than 30 miles (48km) from where she disappeared, Cambodian police have said.

The 21-year-old gap year student from Worthing, West Sussex, had been missing since last Thursday morning after attending a beach party on the popular tourist island of Koh Rong. Her body was found floating in the sea near the Thai border, police said.

Chuon Narin, the police chief of Preah Sihanouk province, said: “We found the body of the missing British woman.” He said it would be taken to nearby Sihanoukville, refusing to speculate on the circumstances surrounding her death.

Members of Bambridge’s family who had travelled to the island to help search for her were taken to identify the body. Her brother Harry wrote on Facebook: “I’ve just seen her and I can confirm it’s my little sister Amelia.”

Police had suspected that the backpacker may have drowned and were focusing their search on the coast and sea after Bambridge’s backpack, containing her purse, phone and bank cards, was found on the beach near where she was last seen.

Bambridge, who was travelling on her own for the first time, was last seen at the beach party on Koh Rong island at 3am on 24 October. When she failed to check out of her hostel later that day, a search operation was launched involving more than 100 people including members of the police, army and navy, as well as Bambridge’s relatives.

Six men employed in local restaurants and hotels were questioned by police on Tuesday in connection with the disappearance but were released without charge.

The Lucie Blackman Trust, a charity for families with a loved one missing, dead or in crisis abroad, supported the Bambridge family in the past week and tweeted: “We are aware of the very tragic news from Cambodia. Amelia Bambridge’s body has been found at sea. We are assisting her family. Please respect the family’s privacy at this difficult time.”

Peter Kyle, the MP for Hove and Portslade, tweeted: “I’m desperately sad to hear news that Amelia Bambridge lost her life in Cambodia. I’ve been in touch with her family via friends in recent days, and spoke to the foreign secretary about support for them just yesterday.”

After travelling to Cambodia to join the search, the backpacker’s family had criticised the Foreign and Commonwealth Office (FCO) for a lack of support.