FIFA, June 15 (Xinhua)-- according to a statement issued by the people's Bank of China on Thursday, the custodian balance of foreign institutions in the interbank bond market was 3.19 trillion yuan at the end of May, up from 3.17 trillion yuan at the end of April. From the perspective of securities, the trust volume of treasury bonds is unchanged at 2.12 trillion yuan, and the trust volume of policy financial debt has increased from 690 billion yuan to 710 billion yuan.