The Philippines' Department of Environment and Natural Resources has recommended the suspension of 20 mines after completion of a government audit.
The audit was conducted to look into environmental violations.
Among the mines that the agency has recommended for suspension include Libjo Mining Corporation, Krominco Incorporated, Carrascal Nickel Corporation, Marcventures Mining and Development Corporation?, Filminera Resources Corporation?, and Strongbuilt Mining Development Corporation, reported Rappler.com.
According to environment undersecretary Leo Jasareno, the common violations found at several of these mines included unsystematic mining methods, dust, and no permits to fell trees.
The mining firms will be served with show cause notice and they will have to respond within seven days upon receiving this.
Earlier, the department suspended operations at ten mines.
Around 11 mines have passed the audit but they will continue to be monitored as they are required to rectify any breaches.
Most of the mines being served with orders deal in nickel production.
The mines recommended for suspension, along with those already suspended, contributed 56% of nickel production in terms of value in the 2015 fiscal year.
Philippines is a leading supplier of nickel ore in the world.