BEIJING, Dec. 18-- In the first 10 months of this year, Chinese authorities broke up 27 "underground banks" illegally trading foreign currency and transferring money across borders.

The exchanges amounted to about 65 billion yuan (10.6 billion U.S. dollars), Zhang Shenghui, head of the Supervision and Inspection Department under the State Administration of Foreign Exchange (SAFE), said Thursday.

Joint operations between the administration and police resulted in the arrest of more than 90 suspects, Zhang said at a press conference in Beijing.

Between September and October, the SAFE cooperated with other agencies to uncover more than 62 billion yuan in illegal transactions, Zhang told reporters.

"Several days ago, we busted a huge underground bank and arrested 57 suspects," said Zhang.

"China will step up efforts on fighting underground banks to safeguard the economic and financial safety," Zhang added.