MEXICO CITY - Mexico’s government plans to seek more than $500-million from Canadian miner First Majestic Silver in what it says are owed taxes for artificially keeping its silver prices low over the past decade, two sources told Reuters.

Audits dating back to 2010 show that the company owes about 11-billion pesos ($534.36-million), the sources said.

So far, Mexico’s Tax Administration Service, or SAT, has sought 5.5-billion pesos ($267.18-million) in tax debt, with the remaining half of the total yet to enter into formal disputes, according to the sources.

Officials are also doubling down on an effort to criminally prosecute First Majestic’s local unit, Primero Empresa Minera, for tax fraud related to the scheme, even after a judge held off on filing charges on Thursday, the sources and another person with direct knowledge of the case said.

Under President Andres Manuel Lopez Obrador, authorities have taken a hardball approach to squeezing taxes out of companies, warning that tax dodgers could face criminal charges and jail time.

The Mexican leader has threatened to personally expose companies with major tax debts, and has called out Canadian mining firms in particular, without naming them.

First Majestic, a Vancouver-based company that owns three working mines in Mexico with another eight in various stages of development, did not respond to a request for comment.

The company has previously said it has made several proposals to resolve taxation disputes with Mexico, and its latest filings show that Mexico’s tax authority has called for $219-million in reassessments.

According to the government’s analysis, Primero Empresa Minera, which First Majestic bought in 2018, set its silver prices below market value in a system similar to transfer pricing used by multinationals to shift profits to low tax havens.

Mexico’s government won one battle against First Majestic in September with a court ruling that nullified Primero Empresa Minera’s pricing arrangement. First Majestic has said it would appeal the decision.

Officials last year also drew up criminal charges, in line with a recent reform that classifies tax fraud over 7.8-million pesos as a serious crime. According to an official document dated April 2020, reviewed by Reuters, prosecutors sought to recover from Primero Empresa Minera 426.3-million pesos ($20.71-million) in taxes owed in 2015 alone.

A judge in the northeastern state of Durango however declined to file charges last week, saying the tax authorities’ audit of the company was incomplete. Prosecutors have appealed the ruling, arguing the full audit was not necessary, said one of the people familiar with the case.

SAT said it would not comment on ongoing investigations.

The finance ministry’s tax prosecutor Carlos Romero declined to comment on First Majestic or Primero Empresa Minera. However, in circumstances when a full audit is requested, he said the prosecutor’s office could file a fresh complaint once the audit is complete.

“We fight to the very end,” he said.

Still, a decision on the appeal could be months away.

First Majestic’s shares surged more than 30% after Bloomberg reported on the court’s decision, the same day as a surge in silver stocks.

Mexican tax authorities reaped payments from nearly 900 large companies last year in their bid to boost state coffers in the country with the lowest tax take in the Organisation for Economic Cooperation and Development. In two of the biggest deals that were made public, Walmart’s Mexico unit and Coca-Cola bottler Femsa forked over nearly 17-billion pesos.