A tragic midair collision between two helicopters on May 17 claimed the lives of all five people onboard. The crash occurred near Eura Airport in southwestern Finland, in a wooded area close to the town of Kauttua.

According to Finnish authorities, both helicopters were privately registered outside of Finland and had been flying from Tallinn, Estonia, en route to Piikajärvi in the Kokemäki region. The crash happened around 12:35 p.m. local time. Emergency responders arrived quickly, but all five occupants—two in one helicopter and three in the other—were pronounced dead at the scene.

The helicopters, both Robinson R-44 models, were completely destroyed. The wreckage was found roughly 300 feet apart. The crash site has since been cordoned off as officials conduct a full investigation.

Finland’s National Bureau of Investigation (NBI) is leading the inquiry in coordination with the Southwestern Finland Police Department and Estonia’s authorities. Investigators from Finland’s Safety Investigation Authority are also involved. The focus right now is on the helicopters’ flight paths—specifically their altitude and the distance between them at the time of the collision.

The remains of the helicopters have been transported to Turku, Finland, for further examination. Autopsies will also be conducted there.

Although Finnish officials have not released the victims’ names, Estonian media identified three of them as prominent businessmen Oleg Sõnajalg and the couple Priit and Lilit Jaagant.

Tiina Bieber, a spokesperson for Finland’s Safety Investigation Authority, stated it’s too early to determine whether the crash was caused by pilot error or mechanical failure. Authorities say the investigation could take anywhere from nine months to a full year.