text_combined: el paso update el paso line 1103 el paso restart approval switched ops national transportation safety board ntsb ntsb currently investigating explosion determine cause blast cause established project shift back ops begin analyze data tests el paso currently running point ops may request el paso either rerun certain tests perform repairs individual ops charge el paso south mainline indicated 3 lines investigated tested ops begin analyze test data one line time ex line 1103 completely tested analyzed cleared use following steps lines 1100 1110 source indicated lines tested repaired current pressure system increase instead maintained currently developing sources ntsb following information cause action 1103 timeframe determine cause action