As a result of the increased demand and tightening restrictions on exports of the metals from China, some countries are stockpiling rare-earth resources. Searches for alternative sources in Australia, Brazil, Canada, South Africa, Tanzania, Greenland, and the United States are ongoing. Mines in these countries were closed when China undercut world prices in the 1990s, and it will take a few years to restart production as there are many barriers to entry. One example is the Mountain Pass mine in California, which announced its resumption of operations on a start-up basis on August 27, 2012. Other significant sites under development outside of China include Steenkampskraal in South Africa, the world's highest grade rare earths and thorium mine, which is gearing to go back into production. Over 80% of the infrastructure is already complete. Other mines include the Nolans Project in Central Australia, the Bokan Mountain project in Alaska, the remote Hoidas Lake project in northern Canada, and the Mount Weld project in Australia. The Hoidas Lake project has the potential to supply about 10% of the $1 billion of REE consumption that occurs in North America every year. Vietnam signed an agreement in October 2010 to supply Japan with rare earths from its northwestern Lai Châu Province.