A power breakdown affected large parts of Maharashtra, Goa and Gujarat on Wednesday.
"Due to the suspected fault in Maharashtra State Electricity Board System coupled with the prevailing low voltages at many strategic locations, there was a grid disturbance in Western region at 10:28 am, leading to a power breakdown," Power Grid Corporation of India Limited General Manager Anjan Roy said.
Everything was normal by 1305 IST, with the synchronisation of the 400KV Gandhar-Padghe line, he said.
Mumbai was spared due to the immediate islanding by the Tata Power Company and was ensured power supply by TPC and Reliance's BSES.
But Navi Mumbai and cities like Pune and Kolhapur were crippled by the failure.
Train services stopped on the Igatpuri-Bhusawal section and several express, mail and goods trains were delayed by more than an hour.
State Energy Minister Dilip Walse-Patil asked the Central Electricity Authority to investigate the failure and submit a report within a month.
The state government also asked the CEA to suggest remedial measures.
On October 6, a similar disruption had occurred on the Padgha-Kalwa 400KV line and a probe had revealed improper maintenance of the line, an MSEB official said.