She said “nothing had seemed unusual” in the family’s last contacts with him.
But she said his phone had been off since 8 August, and there has been no response to emails from his family, and no activity on his social media accounts.
Anton’s friends in Colombia were also reported not to have seen or heard from him.
The only contact the family has had from Colombian authorities was confirmation that a missing person case had been opened, she said.
“It is not a good enough process for families to go weeks and weeks without engagement,” she said.
“Because we’re not being given any updates the anxiety and stress is really building.
“My mum is feeling very unwell, I can see she isn’t coping with it.”