She said all permits given to the project will be reviewed "but we will observe due process".
Officials at Sagittarius Mines Inc, owned by local investor Alcantara Group, which has control of Tampakan, did not immediately respond to requests for comment.
A staunch environmentalist, Lopez said the government has suspended operations of seven domestic mines for failure to meet environmental regulations.
Lopez began an audit of all Philippine mines on July 8 as the new government led by President Rodrigo Duterte vowed to shut operations causing environmental harm.
"I do suspect that we'll probably close more mines given the number of complaints. I have the support of the police and military to run after those violating environmental laws," Lopez said.
Lopez is particularly against the use of open pits to extract minerals, earlier describing it as "madness" even to consider the method in the resource-rich Philippines because of the environmental impact.
Many mineral producers in the Philippines use open-pit mines, which are allowed under the country's mining laws.
The Philippines is the biggest supplier of nickel ore to China, where the metal is used to manufacture stainless steel.
The suspension of some Philippine nickel mines has pushed global nickel prices to an 11-month high of $10,900 a tonne on July 21.
Discovered in the early 1990s, Tampakan has yet to go into commercial operation and only secured an environmental clearance in 2013.
Sagittarius Mines this year was hoping to obtain other necessary approvals, including land access, to enable the project to proceed to construction, according to the company's website.