Binance, the world’s biggest crypto exchange, said on Tuesday it had “temporarily paused” withdrawals of the major stablecoin USDC.

“On USDC, we have seen an increase in withdrawals,” Binance’s chief executive Changpeng Zhao tweeted at around 0820 GMT.

Swapping USDC Coin with two other crypto tokens – Paxos Standard and Binance USD – requires using traditional dollars at a bank in New York, Zhao added. “The banks are not open for another few hours. We expect the situation will be restored when the banks open.”

The swaps are “1:1 conversions, no margin or leverage involved. We will also try to establish more fluid swap channels in the future,” he added.

Binance said in a separate tweet the halt was due to “token swap” – where digital token holders exchange their crypto coins, typically over different blockchains.

Binance said in September it would automatically convert user balances and new deposits of USD Coin and other stablecoins Pax Dollar and True USD into its own stablecoin, Binance USD.

Binance did not immediately respond to a request for comment.