New evidence continues to surface in the investigations into what caused the energy crisis that plagued California in 2000 and 2001, as a former electricity trader for the now-defunct Enron Corp. pleaded guilty to inflating prices during that period. The admission will likely strengthen the case being made by state officials for billions of dollars in refunds for California energy customers.

Timothy Belden, who worked as head of Enron’s western power trading unit in Portland, agreed to plead guilty to one count of conspiracy to commit wire fraud in the most recent development in the Federal Energy Regulatory Commission’s and Commodity Futures Trading Commission’s investigation into energy trading practices during California’s power crisis.

California is seeking $9 billion in refunds for alleged price-gouging by several large energy firms.