A US probe into the security of video conferencing service Zoom widened, with state attorney generals concerned about the privacy and protection of users as the system’s popularity soars during Covid-19 (coronavirus)-related lockdowns, CNBC reported.

Connecticut attorney general William Tong announced on 3 April at least two other states, including New York and Florida, had joined an investigation, following a number of reports of unidentified individuals invading meetings.

Tong was reportedly a victim of this, with the chat section of one conversation apparently filled by obscene messages.

It is unclear whether the privacy of people using mobile versions of Zoom have been compromised.

The Verge reported last week Zoom had suspended the launch of new features for three months to concentrate on boosting privacy, and announced changes to its mobile app including password-protection for meetings and a requirement for hosts to accept participants before they connect.

On 1 April Zoom CEO Eric Yuan announced the service had 200 million daily participants in online meetings during March.

CNBC stated the company added 2.2 million users between 1 January and 24 February, compared with 640,000 in 2019 as a whole.

The spike in use coincides with a rise in people working from home after governments throughout the world issued lockdown orders designed to help curb the spread of Covid-19.