SAN FRANCICSO (AP) — A lead attorney probing a deadly pipeline explosion for state regulators says he quit the investigation because he disagreed with managers handling of the case.

Attorney Robert Cagan called the California Public Utilities Commission's recommended punishment for the responsible utility "unlawful." KQED quoted an email Cagan sent the radio station Thursday.

Cagan and three other lawyers who also quit the investigation were the commission's main experts on the 2010 explosion that killed eight and destroyed 38 homes. The resignations came just before the commission was set to announce the penalty for Pacific Gas & Electric Co.

Cagen's boss has called for PG&E to pay $2.25 billion, some of which can be deducted from the utility's tax bill.