The pilot and co-pilot of the small plane that crashed Sunday afternoon near London Southend Airport were Dutch nationals, Sky News reported. According to the British broadcaster, the families of the two Dutch crew members have been notified.

Authorities confirmed Sunday that all four occupants of the aircraft died in the accident. During a news conference, police said the identities of the victims had not yet been officially established, but they believed all four were foreign nationals.

Sky News reported the victims were three men and one woman. Their ages were not yet known. The woman was said to be a nurse from Chile, while one of the men was a doctor from another European country. The remaining two men were identified as the Dutch pilot and co-pilot.

Other British media outlets, including The Guardian, reported that the aircraft was equipped with medical systems and configured for transporting patients.

The plane belonged to the Dutch aviation company Zeusch Aviation and was on its way to Lelystad Airport in the Netherlands at the time of the crash.

Earlier on Sunday, the aircraft had flown from Athens, Greece, to Pula, Croatia, before continuing to Southend with a planned return to Lelystad that evening.

The British Air Accidents Investigation Branch is leading the investigation into the crash. The Dutch Safety Board said Monday it is part of the investigation team but does not have personnel on site in England.

Reporting by ANP and NL Times