Applications to mine bauxite in Terengganu have been frozen after the local government said it wanted to safeguard against pollution, underscoring the risks associated with a boom in production to feed China’s aluminum smelters.

“As of now, the state government is not prepared to approve bauxite applications in the whole state of Terengganu,” Johan Ibrahim, deputy director of the land and mines office, said in an emailed reply to questions. “This is to protect the environment.”

Malaysia has become China’s biggest supplier of bauxite after Indonesia halted mineral shipments in January 2014 to spur investment in domestic smelters.

The rapid expansion in mining has drawn scrutiny after reports that bauxite residue is polluting the environment with radioactive material.

State news agency Bernama first reported Terengganu’s suspension earlier this month, citing Menteri Besar Ahmad Razif Abdul Rahman.

Most of the nation’s bauxite is mined in Pahang, a state neighbouring Terengganu on the east coast of peninsular Malaysia.

The Department of Environment (DOE) sent samples of earth, water, and bauxite from Pahang to the Atomic Energy Licensing Board (AELB) to test for contamination, the New Straits Times newspaper reported in Aug 6, with the results expected in a month.

Emails sent to the DOE and the AELB seeking comment were not immediately answered.

China’s imports of bauxite from Malaysia surged 24 percent to a record 2.28 million tonnes in July from a month earlier, according to Chinese customs data.

That brought the total for the first seven months of the year to 10.2 million tonnes, more than triple shipments for the whole of 2014.