According to a note issued by the police of the canton of Thurgau, a helicopter accident occurred today in Sitterdorf, the second one within a few days in this Canton. 
Shortly after 11:00 a.m., a Robinson R44 Raven II with call-sign HB-ZWN crashed while approaching the airport. The helicopter came to rest upside down on its side. The pilot, a 30-year-old woman, and the three passengers, aged between 23 and 60, were not injured. The helicopter was severely damaged.
Under Article 98 of the Aviation Act, the Office of the Attorney General of Switzerland is responsible for the prosecution of offences committed on board an aircraft.
In order to clarify the exact course of events and the cause of the accident, experts of the Swiss Transportation Safety Investigation Board (STSB) have opened an inquiry.
The investigation is being conducted with the support of the public prosecutor's office and the Thurgau cantonal police.
An official from the Office for the Environment inspected the accident site for possible soil pollution.