The PSA has decided to conduct an investigation due to, among other factors, the significant potential of the incident. The leak occurred in connection with valve testing on the drilling, production and accommodation facility HMP1 on the Heimdal field. It has not yet been determined how much gas leaked out, but the gas leak was substantial and resulted in a serious situation on the facility. There were 98 people on the facility when the leak was discovered. No one was injured in the incident. The purpose of the investigation is to ascertain the course of events and identify trigger factors and underlying causes. The investigation will result in a report which will be published at www.ptil.no.