A federal grand jury is investigating at least one new instance of obstruction of justice against PG&E in connection with a fatal explosion in San Bruno, and the utility also raised the specter in court papers on Monday that it could be harmed by media publicity before its trial begins March 22. "The government has disclosed in a telephonic hearing before this court that a current, ongoing grand jury is investigating potential obstruction" against PG&E. That grand jury probe is in connection with an already existing obstruction of justice that is one of the 13 charges that PG&E must face in the case.