Stock market authorities in China opened a probe into a potential conflict of interest in a long-awaited IPO of mobile payment giant Ant Group, Reuters reported, a move likely to further delay a listing already in the works for more than two years.

The news publication’s sources said the China Securities Regulatory Commission was looking into a plan for Ant Group’s mobile payment platform Alipay to be the only third-party channel retail investors could use to buy into five funds committed to taking part in the IPO.

In September Ant Group began filing formal paperwork for the dual-listing IPO, with shares exchanged in Hong Kong and Shanghai, having outlined its plan in July. Reuters estimated the sale could raise $35 billion, breaking the global record for a public listing.

The company, previously known as Ant Financial, has long been expected to IPO shares with firm plans reportedly put on ice in 2018. At the time Financial Times cited regulatory concerns and unspecified issues with the business itself.

In addition to running one of two dominant mobile payment platforms in China, Ant Group has a number of partnerships with, and investments in, mobile payment providers across a wide range of markets. It also provides enterprise services and a range of consumer-facing financial products covering sectors including credit and wealth management.