Police in Malaysia said they were "very certain" a body found on Tuesday was that of the missing teenager.
The body was found following a 10-day search for Nora Quorin, who went missing from the Dusun eco resort in Seremban, about 50 miles south of the capital Kuala Lumpur on 4 August.
Nora, who suffered learning difficulties, lived in London with her French father and Irish mother.
Malaysia’s deputy police chief, Mazlan Mansor, said he had no doubt the body was that of Nora.
Announcing the reward on Monday, her mother said Nora was "so precious to us" and said, their "hearts are breaking".
On Tuesday, 13 August, police chief Mohammed Yusop said: “I can confirm a body has been found in the Betembum mountains. It is not in an accessible place.”
The body was reportedly found near a waterfall.
The Lucie Blackman Trust, which was set up in the wake of the murder of a British hostess in Japan in 2000, said: "At this time we cannot confirm it is Nora. However it sadly seems likely. Investigations are underway to confirm identity and cause of death."
Nora’s family said they were convinced she had been abducted but the Malaysian police have said there were no signs of foul play.
An autopsy will now be carried out and should clarify if she was murdered or died as a result of an accident or animal attack.
The Malaysian jungle is home to the Malayan tiger and also several species of snake.
Local shamans had conducted various rituals in an effort to locate Nora.