The exterior of the Federal Reserve building in Washington, DC.

A virtual event with Federal Reserve Governor Christopher Waller was canceled on Thursday after the Zoom videoconference was “hijacked” by a participant who displayed pornographic images.

“We were a victim of a teleconference or Zoom hijacking and we are trying to understand what we need to do going forward to prevent this from ever happening again. It is an incident we deeply regret,” said Brent Tjarks, executive director of the Mid-Size Bank Coalition of America (MBCA), which hosted the event via a Zoom link. “We have had various programs and this is something that we have never had happen to us.”

He said that he suspects one of the security switches that mutes those watching an event was set incorrectly, but he was not yet sure of the details. The decision to cancel was made in consultation with the Fed after the intrusion.

A few minutes before the event was to start, one participant using the screen name “Dan” began displaying graphic, pornographic images, according to a Reuters reporter on the call.

Microphones and video were not muted by the organizer upon joining.

More than 220 participants were on the Zoom call at one point before it was terminated. Two spokeswomen for Zoom did not immediately return calls requesting comment.

Zoom use mushroomed during the pandemic. It came under fire over privacy and security issues, including incidents of “Zoom bombing” in which uninvited users entered and disrupted meetings.

In March 2020, the Federal Bureau of Investigation’s Boston office issued a warning about Zoom, telling users not to make meetings on the site public or share links widely after it received two reports of unidentified individuals invading school sessions.

In response to the disruptions, Zoom rolled out major upgrades, including end-to-end encryption for video calls.

The Fed said the event, which was to feature a speech by Waller as well as a question-and-answer session, was canceled due to “technical difficulties.”

Fed events are typically highly choreographed and security is usually tight.

MBCA’s roughly 100 members include banks with between $10 billion and $100 billion in assets.