Coal workers affiliated to five trade unions had gone on strike from July 2-4.
The MCL notice also said that Deputy Labour Commissioner, Kolkata, has been seized of the matter for conciliation under provisions of Industrial Disputes Act, 1947.
Of the around 20,000 workers of MCL, 15,000 to 16,000 workers were on strike so did not report to work, a company official said.
"Since the strike has been under conciliation, participation in such a strike is in contravention to Section 10 (3) of the Industrial Disputes Act, 1947 and as such, is prohibited....and is an illegal strike, as per clause 24(1) (ii) of the Industrial Disputes Act, 1947," the notice said.
State-owned Coal India (CIL) on Tuesday said it managed to clock an average daily production of 44 per cent and average attendance of nearly 36 per cent during the three-day strike.
This calculation of average is based on the average of 10 days prior to July 2 -- the first day of the three-day strike.
Coal India accounts for over 80 per cent of domestic coal output.
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