The Cullen Inquiry was set up in November 1988 to establish the cause of the disaster. It was chaired by the Scottish judge William Cullen. After 180 days of proceedings, it released its report "Public Inquiry into the Piper Alpha Disaster" (short: "Cullen Report") in November 1990. It concluded that the initial condensate leak was the result of maintenance work being carried out simultaneously on a pump and related safety valve. The inquiry was critical of Piper Alpha's operator, Occidental, which was found guilty of having inadequate maintenance and safety procedures, but no criminal charges were ever brought against the company.