Two months ago, global investors including Warburg Pincus, Carlyle, Temasek and GIC were on the cusp of a massive windfall from what would have been the world’s largest initial public offering.

Now, returns on the hundreds of millions of dollars they invested with Ant Group Co. are in jeopardy. On Sunday, China ordered Ant to reexamine its fintech businesses — spanning from wealth management to consumer credit lending and insurance — and return to its roots as a payments service.

While the central bank’s statement was short on specifics, it presents a serious threat to the growth and most lucrative operations of billionaire Jack Ma’s online finance empire. Regulators stopped short of asking directly for a breakup of the company, yet stressed it was important Ant "understand the necessity of overhauling its business” and told it to come up with a plan and timetable as soon as possible.