San Juan, Nov 10 (IANS): Power was being gradually restored to San Juan after a massive new outage struck the hurricane-battered Puerto Rican capital city, the media reported.

The problem was with a failure on a main north-south transmission line, CNN quoted Fernando Padilla, an official with the Puerto Rico Electric Power Authority (PREPA), as saying on Thursday.

"It was a mechanical issue on the line, could have happened at any line... It's being patrolled and repaired by PREPA."

Power went out about 11.30 a.m. (local time) and was partially repaired on Thursday night, said Ricardo Ramos Rodriguez, Executive Director, PREPA.

PREPA spokesman Carlos Monroig said 25 per cent of power was back and he expects 42 per cent of power to be restored by Friday morning.

Much of Puerto Rico has been without power since Hurricane Maria battered the island on September 20.

Maria left at least 54 people dead, destroying the island's power grid and causing a massive humanitarian crisis that further worsened the economic crisis.

So far, only 30 per cent of the people have got their power supply back.