Marcin Bielecki/PAP

Polish police have launched an investigation after a police helicopter brought down a power line during a military picnic attended by the public.

The incident occurred on August 20 near the central town of Ciechanow during an event to mark the 103rd anniversary of the Battle of Sarnowa Gora.

Video taken at the time shows the Black Hawk helicopter take off from a field with members of the public looking on. As it made a low pass over onlookers it downed a power line, causing panic and alarm among the crowd.

“In accordance with procedures, the relevant authorities have been notified, including the prosecutor’s office and the State Aviation Accident Investigation Commission,” the police said in a statement published on the National Police Headquarters (KGP) website.

“The necessary procedural steps were also carried out on the spot, and the collected evidence will be immediately transferred to the prosecutor’s office,” the statement also said.

No one was injured in the incident.