PGE stock

PG&E shares plunged $4.03 on Friday to $44.21 one day after the blast. Investors continued taking profits on Monday, but the stock then recovered to close up a nickel. Still, the ultimate impact will depend on the investigation's results.

Shares in PG&E, California's largest utility company, tumbled Friday after one of its natural-gas pipelines exploded in San Bruno, Calif., killing at least four people and destroying 38 homes.