NEW : Regulators could impose the recommended fine in late 2018 . The San Bruno , California , explosion killed three people . The blast damaged dozens of homes in the San Francisco suburb . A $ 2.25 billion fine would be largest state penalty , regulator said .
NEW : Regulators could approve the recommended fine in late summer . The San Bruno , California , explosion killed 8 people . The blast destroyed dozens of homes in the San Francisco suburb . Proposed $ 2.25 billion fine would be largest state penalty , regulator says .