A major power failure paralysed normal life and brought train services to a standstill in the entire north and south Mumbai on Tuesday night.
Power supply was disrupted around 2130 hrs due to 'technical faults' in the distribution and supply network.
"The problem was due to fault in Tata Power company's stations in Trombay," a BEST spokesperson said.
Power supply was restored for a while, but soon the systems collapsed, plunging parts of city into darkness again.
An official of Reliance Energy Ltd, which predominantly provides power to the suburban region, said certain pockets in eastern part of the city 'where we depend on Tata Power were affected'.
"We are currently drawing part of our requirements from our plant at Dahanu," he added.
Power is being restored in phases in city and suburbs, Tata Power official said. Power was restored at 2315 hrs.
"TPL has ordered a technical investigation into the cause of the power failure and the findings would be known tomorrow morning," a company official said.
This is the second time that the city has been affected due to power failure this year. On February 5, Chandrapur-Koradi 400 KV line burst at around 1420 hrs, triggering a cascading effect, which resulted in tripping of almost all the power stations in the state.
A spokesperson of Reliance Power Ltd, which supplies the suburbs, said, "We had to draw power from our generation unit at Dahanu to ensure steady supply though some pockets like Chembur remained without electricity."
Railway network was limping back to normalcy with priority supplies from TPL, while power was being restored in phases to residential and commercial areas.
BEST spokesperson said about 75 per cent of south Mumbai is now getting normal supplies and work is on to improve the situation in central part of the city.
