Three BBC journalists had been questioned by Swiss police for illegally flying a drone at the World Economic Forum in Davos last month, The Guardian reported on Tuesday. The journalists, who were working with chief business correspondent Linda Yueh, were briefly held for questioning after launching the aerial craft in a no-fly zone.

The Forum, with its security budget of $9 million, was heavily monitored and secured with 26 miles of fencing and 5,000 Swiss troops. A no-fly zone was declared within 25 miles of the meet that was attended by about 2,500 world leaders and dignitaries. The security breach comes shortly after terror attacks in Paris, and threats throughout the continent.

The BBC admitted the incident when contacted by The Guardian. A spokesperson reportedly said that “in Davos during the World Economic Forum a BBC team mistakenly took a drone into a no-fly zone area. Three members of staff were briefly questioned by police and it is still to be determined by the Swiss authorities if the BBC will pay a fine.”

The BBC is one of only a few media organizations to operate its own drone journalism team, and has previously used drones for capturing footage from the Auschwitz concentration camp and Stonehenge.

The BBC has principally been known to use “hexacopter” style drones. It is unknown whether this is the model of drone that was flown at Davos, The Guardian reported.

Broadcasters and private individuals are increasingly using drones to capture footage as the cost of flying unmanned aerial vehicles declines. Their widening popularity has led to increased concerns about safety. ABC affiliate WFAA reported on Monday that a recent building implosion in Dallas was captured by four unknown drones hovering near the scene, in what authorities believe to be a serious safety breach.

In December, a drone almost collided with an Airbus A320 at London’s Heathrow airport, The Daily Mirror reported.

The Davos conference took place over three days at the end of January. Delegates, including chief executives and country leaders, had to pass through many layers of security, as well as background checks, before being admitted to the conference.

The World Economic Forum is a Swiss nonprofit foundation, founded in 1971 to serve as a place to shape agendas across regions and industries.