The request comes amid concerns about the deal's funding triggered by the possible withdrawal of a crucial loan from China Development Bank (CDB). Reuters reported on Tuesday that CDB is reconsidering its offer to finance a substantial portion of the deal, after the Chinese and Hong Kong media said funding from CP's first installment came from people not affiliated with CP. The company has denied the reports.

"The CIRC has received an application from Ping An Group regarding the stake transfer, conducted a preliminary review according to rules, and notified the company to provide additional materials," the CIRC said in an emailed statement to Reuters on Thursday, without specifying what additional information it was seeking.

The CIRC has set a deadline of February 1 for final approval of the transaction, which would have HSBC exit from a lucrative investment that it now sees as offering no long-term strategic benefits.

The deal requires approval because HSBC held 16 percent of Ping An's shares, more than the 5 percent threshold above which prospective owners need CIRC permission. CP Group planned to buy the stake from HSBC in two stages: an initial outright purchase of 20 percent of the shares on offer, and then a CDB-funded second offer for the remaining 80 percent.

It is this second stage that is now in jeopardy as CDB wavers in its commitment and CIRC investigates the structure of the whole transaction. Late last month, media reports in China and Hong Kong said the first CP payment came from funding sources not directly tied to the Thai conglomerate, contrary to the terms of the agreement.

"The transaction is undergoing the normal approval procedures and there is nothing further to disclose at this time," Ping An Insurance said in an e-mailed statement on Thursday.

The failure of the deal would be a blow to HSBC Holdings Plc and an embarrassment to the various parties involved in a deal which at $9.4 billion was set to be the largest ever inbound acquisition deal in China.

CP spokeswoman Suthana Hongthong said the deal is still on. "Everything is still in process," she said without giving details.

(Reporting by Samuel Shen and Kazunori Takada; Additional reporting by Lawrence White and Khettiya Jittapong; Editing by Ryan Woo)

• A Permanent Economic Emergency