The July fire on the Piper Alpha platform in the North Sea that killed 167 men apparently started with explosions in the main gas compressor unit, according to an official British report. The first blast July 6 probably damaged pipes carrying gases under pressure, the interim report by the Energy Department said. The hydrocarbons then ignited, causing fires and more explosions. The report said the blasts apparently cut electrical power and disabled key control and communications facilities on the platform, operated by the Occidental Petroleum Corp. The author of the report, Jim Petrie, said new safety regulations are being drawn up.