India's largest oil producer Oil and Natural Gas Corporation on Thursday said it was back to doing normal business and all its workers returned to their jobs after a day's non-cooperation agitation against Monday's helicopter accident.

"Today we observed ONGC Day. A function was held at our Mumbai office where the death of 25 people (two people are still missing) in the helicopter crash was mourned. After that workers were back at work," a senior company official told PTI.

The official, who did not wish to be identified, said operations in the Mumbai offshore region, which produces 50 per cent of country's total crude oil, were normal.

"Yesterday, we saw some employees staging a sit-in dharna at corporate office in Mumbai but today even that is not happening. All workers are doing their duties," he claimed.

ONGC executive director and Bombay High asset manager Kharak Singh told PTI from Mumbai, "We are getting cooperation from all our employees in producing oil and running infrastructure. No untoward incident has been reported."

Mumbai offshore fields, comprising Bombay High, Heera and Neelam fields, would produce over 290,000 barrels of oil on Thursday as against about 260,000 barrels produced on Wednesday.

"Wednesday we lost 12-15 hours of production on some wells because of delays in mooring and de-mooring oil tankers.

"It took more time due to turbulent waters during monsoon, so we had to shut a few wells.