MINNEAPOLIS (AP) — PolyMet Mining Corp. is offering Minnesota a $544 million package of financial assurances to serve as an insurance policy to protect taxpayers from having to cover the costs of shutting down and cleaning up the copper-nickel mine it proposes to build in northeastern Minnesota.

The company said in an updated permit application Wednesday that the package of bonds, letters of credit and a trust fund will be sufficient to cover all the costs, including treating the mine's wastewater for as long as necessary.

Financial assurances have been one of the most contentious issues in the fight over the proposed mine near Babbitt and processing plant near Hoyt Lakes. Environmental groups say copper-nickel mines elsewhere have a long track record of going bankrupt and leaving taxpayers stuck with the cleanup costs.