An NDRC statement did not specify where the supervision teams, which it jointly dispatched with the National Energy Administration, had been sent to. However, it said their work was manly on-site supervision and included a focus on implementing policies to increase coal production and supply.
Top coal consumer China has been striving to boost coal production to meet surging demand as prices for the fuel hit record highs. It has also attempted to rein in high prices for other key commodities, including by releasing state reserves.
In a separate statement, the planner lowered the minimum coal inventory power producers are required to keep during peak demand season to seven days, and a maximum at 12 days worth of use.
It did not give a comparative figure.
"By adjusting lower the coal inventory requirement for peak season. ..it helps to free up supplies and stabilise prices," said the planner.
Last week the country's leading coal associations urged miners and power firms to sign up additional mid-to-long term contracts on top of existing agreements and thermal coal should be prioritised.
(Reporting by Tom Daly, Eve Wu and Chen Aizhu; Editing by Mark Potter and Louise Heavens)