Uncertainty swirls around China Evergrande as a payment deadline passes.

The possible collapse of the real estate giant China Evergrande shook markets around the world earlier this week. But on Thursday, amid uncertainty over whether it met a critical payment deadline to its lenders, the market rallied.

Evergrande’s Hong Kong listed shares, which have been on a firm downward trajectory, soared by a head-scratching 18 percent. Hong Kong’s broader Hang Seng Index rallied 1.2 percent.

Investors are now taking bets on whether regulators in the world’s second-largest economy, after that of the United States, will step in to save Evergrande, a corporate behemoth that has been struggling under the weight of more than $300 billion in debt.

So far Beijing has remained tight-lipped, while emphasizing that no Chinese company is too big to fail. In recent weeks, however, a steady flow of negative news from Evergrande has prompted panic and raised fears of a possible economic fallout from an Evergrande default.

Unable to sell off parts of its corporate sprawl or raise fresh cash through the sale of new properties, Evergrande is also facing angry suppliers, home buyers and employees, some of whom have protested and demanded their money.

Evergrande said in a vaguely worded statement on Wednesday that it had reached a deal with investors over a bond payment due for mainland Chinese bondholders without giving any details. It offered no guidance on another payment on $83.5 million that was also due on Thursday for foreign bondholders. The company has a 30-day grace period before the missed payment would trigger a default, according to Bloomberg.

Evergrande did not respond to questions seeking clarity.

Evergrande’s fate and what its failure could mean for China’s economy have divided some of the world’s best known investors. The billionaire investor George Soros recently argued that an Evergrande collapse would set off a broader economic crash, while another billionaire investor, Ray Dalio, argued this week that an Evergrande default was “manageable.”

As China’s economic growth has slowed, officials have stepped in to shore up confidence. The central bank said on Wednesday that it had pumped $18.6 billion into markets. It added another $18.6 billion on Thursday, as officials try to circulate more cash into the banking system.