The Kenyan government has ordered cryptocurrency project Worldcoin to stop signing up new users, citing data privacy concerns.
Worldcoin, founded by US tech entrepreneur Sam Altman, offers free crypto tokens to people who agree to have their eyeballs scanned.
Thousands of Kenyans have been queuing up at registration centres this week to get the currency worth about $49 (£39).
Kenya warned citizens to be cautious giving their data to private companies.
The ministry of the interior has launched an investigation into Worldcoin and called on security services and data protection agencies to establish its authenticity and legality.
In one of the pop-up registration centres in the capital, Nairobi, where hundreds had been lining up for the registration, many had been locked out of the process on Wednesday after the large crowd was termed a “security risk”.
“I’ve been coming here almost three days to line up and register. I want to register because I’m jobless and I’m broke, that’s why I’m here,” Webster Musa told the BBC.
“I came here yesterday. I waited until my phone died. So I came again today but I’ve missed the registration again. I really like Worldcoin because of the money. I’m not worried about the data being taken. As long as the money comes,” added Dickson Muli.
Worldcoin says it cannot say how many people have had their eyeballs scanned in Kenya.
It claims to be creating a new global “identity and financial network”.
“We are creating the world’s largest identity and financial network as a public utility, giving ownership to everyone. And establishing universal access to the global economy regardless of country or background,” a statement on the Worldcoin website reads.
Mr Altman, who founded Open AI which built chat bot ChatGPT, says he hopes the initiative will help confirm if someone is a human or a robot. He also says this could lead to everyone being paid a universal basic income but it is not clear how.