Anna Lightfoot, who was in Central America with the charity Raleigh International, had gone missing on a routine shopping trip along a route she knew well.
Her body was discovered near a dirt track after a four-day search with the aid of army helicopters.
Anna's father David Lightfoot, in Saddleworth, Greater Manchester, said items belonging to his daughter appear to be missing.
"I do not want to speculate about what happened to my daughter but I believe there are suspicious circumstances, as do Raleigh International," he added.
A spokesman for Raleigh International, the organisers of the charity project, said it was mystified by what had happened.
Ms Lightfoot, a qualified countryside warden, had been in Belize for seven weeks and was familiar with the one-hour walk through a banana plantation and a forest where she disappeared. She had also undergone a thorough assessment before leaving Britain.
"Anna wanted a big adventure before she found a serious partner," Mr Lightfoot went on.
"She was very keen on the Belize project. We got a letter from her yesterday, and it was mainly about the project, saying that it was going well. She said she going to stay on in Belize, and she wanted to work in a zoo there. Then she planned to move on and travel around the world.
"We heard the news in the early hours of Wednesday morning. We are absolutely devastated.
"We were more worried about her trip around the world than her time in Belize. The forensic teams will go in next and then I am hoping her body can be flown back."
Ms Lightfoot had arrived in Belize on June 25 as one of 36 volunteer members of staff who were to work with 93 young people from Britain to build a three-classroom school for local children in the village of San Pablo.
She was last seen on Monday afternoon when she was leaving the neighbouring village of Red Bank with provisions for San Pablo. More than 100 villagers, fellow volunteers, soldiers from the British Army base and the Belizean defence force joined the hunt. Her body was 500 metres from the track.
The Central American trip was Ms Lightfoot's first with Raleigh International. But withthe charity, as well as the assessment, she had had regular briefing sessions, and her job as a countryside warden with Tameside council in Greater Manchester made her familiar with the outdoor life.
Raleigh International had organised seven similar expeditions to Belize since 1995. Overall the charity, founded in l984, had sent about 19,000 venturers - young people aged between 17 and 25 - to 35 countries around the world.
In that time there have been six deaths, three members of staff and three venturers. The charity points out it was not found to be at fault in any of the cases. The charity's chief executive, Jamie Robertson-Macleod, said: "Our hearts go out to Anna's family at this very difficult time. We are all very sorry about what has happened."
A Foreign Office spokesman said they were awaiting result of the police investigation, although initial inquiries " suggest nothing untoward".
Belize, on the Caribbean coast of Central America, has a population of barely 200,000 and only two paved roads cutting across a landscape of swamp, forest and farmland. The country was colonised by Britain after a successful war against Spain in 1862.
It was granted self government in 1964, and full independence in 1981. British troops have been stationed in the country to combat territorial claims by neighbouring Guatemala.
A British girl of 15 underwent surgery yesterday after being raped on the Costa del Sol. The girl, on holiday with her family, was attacked on the Burriana beach at Nerja near Malaga after a midnight party.