REPORT: 3 arrested in UK insider trading probe
The arrests occurred in the past few months and will be followed by more, according to Bloomberg.
The UK's markets regulator, the Financial Conduct Authority is working with the National Crime Agency on the investigation.
A spokeswoman for the FCA declined to comment.
In May, two men, including a former managing director at Deutsche Bank, were found guilty in the UK's biggest-ever insider trading case.
Martyn Dodgson, the former managing director, and Andrew Hind, an accountant, were convicted by a London jury on Monday after a trial that lasted 12 weeks.
Three other defendants - Grant Harrison, a former managing director at Altium Capital, day trader Benjamin Anderson and former Aria Capital director Iraj Parvizi - were found not guilty.
The convicted men face a maximum of seven years in prison and a sentencing verdict could come as soon as this week.
They were accused of generating more than £7 million in profit, trading on inside information on stocks such as Legal & General, Scottish & Newcastle, and Sky.