Chinese authorities summoned several state-owned banks and other lenders on Friday to clarify details of closely watched industry probes, local media reported.

The investigations by National Association of Financial Market Institutional Investors, an entity governed by China’s central bank that oversees interbank bond sales, are looking into alleged violations including that banks and issuers reach agreed pricing before issuance, Cailian reported, without naming any institutions or saying where it got the information. The association has inquired about the banks’ low underwriting fees on a monthly basis, it said.

China’s credit markets closed out the week trying to digest the implications of the new probes into bond underwriting at several major banks, Bloomberg News reported. Authorities have for years sought to improve the oversight of the debt market by clamping down on practices that unfairly skew prices, inflate demand and mislead investors.

NAFMII said on Tuesday it was probing Export-Import Bank of China for alleged violations in financial bond issuance, and was also looking into alleged violations in debt arranging at China Minsheng Bank Corp.

On Thursday, the agency said it had launched a so-called self-discipline investigation into China Construction Bank Corp. for alleged violations in underwriting services.

READ: China Regulator Steps Up Probes of Bond Underwriting Practices