Federal prosecutors have dropped all but $6 million of a potential $562 million fine levied against Pacific Gas and Electric (PG&E) for safety violations related to the lethal explosion in San Bruno in 2010. The blast killed 8 people and destroyed 38 homes, triggering a massive fire that swept through this southern San Franciscan neighborhood..

U.S. District Court Judge Thelton Henderson issued the order late Tuesday, hours after the U.S. Attorney's Office requested it in a court filing. The judge did not explain his reasoning.

Federal prosecutors will determine how much of the remaining fine of $6 million will be levied if PG&E is convicted of 11 pipeline safety violations and obstructing investigators in the wake of the 2010 blast.

PG&E pleaded not guilty and said its employees did the best they could with ambiguous regulations they struggled to understand. Engineers did not think the pipelines posed a safety risk, and the company did not intend to mislead investigators, PG&E attorney Steven Bauer said during the trial.