MEXICO CITY (Reuters) – The head of Mexico’s mining industry said the new government does not seek to implement drastic changes in the sector, cancel concessions or raise royalties that companies pay to extract minerals.

At the end of last month, shares of Mexico’s main mining companies fell more than 10 percent after the party of new President Andres Manuel Lopez Obrador made a proposal in the Senate that would toughen rules for the sector.

The plan would force the government to obtain indigenous communities’ consent before granting concessions on their lands. Companies could also lose their permits if they do not present an annual report on the projects’ social impact.

But Francisco Quiroga, the undersecretary for mining, said in an interview on Wednesday that the so-called indigenous consultation would be required only for new permits.

“There is a principle of non-retroactivity of the law,” he said. “No rights will be violated, neither those of the communities nor those of the companies.”

Quiroga also ruled out the possibility that the new government, which took office on Dec. 1, would review the country’s nearly 26,000 concessions for anomalies, as Lopez Obrador proposed.

Mexico is the world’s top silver producer and one of the largest producers of copper and gold. The mining sector contributes about 4 percent of Mexico’s gross domestic product.

Quiroga said, for the time being, his efforts were focused on simplifying procedures, promoting new projects and boosting exploration in the sector.