Pacific Gas & Electric is accused of lying to regulators in connection with a fatal pipeline explosion that leveled a suburban Northern California neighborhood in 2010.
The U.S. attorney in San Francisco announced the obstruction of justice charge and 27 related counts Tuesday.
The new indictment replaces a previous indictment that contained 12 counts, but not obstruction.
Prosecutors say PG&E hampered the investigation by lying to regulators immediately after the blast.
The other charges accuse the utility of failing to act on threats in its pipeline system even after the problems were identified by its own inspectors.
The explosion destroyed 38 homes, killed eight people and injured dozens.
PG&E faces hundreds of millions of dollars in fines if found guilty.
-- The Associated Press