MANILA -- The Department of Environment and Natural Resources said 9 suspended mines would be allowed to resume operations if they rectify previous violations of environmental regulations, a move that could boost nickel output in the major supplier of the metal.

The 9 mines were ordered permanently closed in February last year as part of an environmental clampdown on the sector. They appealed the decision, along with 4 other mines, and after a review, Environment and Natural Resources Secretary Roy Cimatu changed closure of the mines to a suspension.

Any re-opening of the 9 mines - 6 of which are nickel - could improve the nation's output of ore going forward, after the disruptions caused by the crackdown that began in 2016. The Philippines is the world's second-biggest nickel ore producer after Indonesia.

"On top of the payment of the fines and penalties, these companies were directed to undertake corrective measures within a timetable," Cimatu said in a statement on Friday.

Failure to do so will mean a reinstatement of the closure order on the mines, he said.

"The sooner they complete the corrective measures, the sooner their suspension will be lifted," Environment Undersecretary Analiza Teh told Reuters in a text message.

The corrective measures include hiring of safety engineers and permit applications for mine discharge, said Teh, and it should take the mines an average of 6 months to complete them.

Cimatu also ordered the permanent closure of two nickel mines and an iron ore producer and the resumption of operations at suspended nickel producer, Berong Nickel Corp, a unit of diversified conglomerate DMCI Holdings Inc.

Shares of DMCI jumped 2.3 percent.

The 3 mines ordered shut for good can file appeals with President Rodrigo Duterte's office, Cimatu said.

Many of the 13 mines stopped operating since being suspended last year, said Wilfredo Moncano, head of the government's Mines and Geosciences Bureau.

The Philippines has 48 metallic mines, with 30 digging for nickel ore, most of which is shipped to top market China, where it is used to produce stainless steel.

Philippine nickel ore output fell 10 percent in the first half of 2018 from a year earlier to 9.43 million tons, government data showed.