Chinese regulators have announced an anti-monopoly investigation of e-commerce giant Alibaba Group, stepping up official efforts to tighten control over the country’s fast-growing tech industries.

The market regulator said it was looking into Alibaba’s policy of “choose one of two”, which requires business partners to avoid dealing with competitors.

The one sentence statement gave no details of possible penalties or a timeline to announce a result.

Chinese leaders have previously said stepping up anti-monopoly enforcement will be an economic priority in the coming year.

They appear to be especially concerned about tightening control over Alibaba and other dominant internet companies that are expanding into finance, health care and other businesses.

Alibaba’s founder Jack Ma is China’s richest entrepreneur and one of the country’s best-known figures.

Regulators earlier forced the suspension of the stock market debut of Ant Group, an online finance platform spun off from Alibaba.

A separate announcement on Thursday said officials of Ant had been summoned to meet with regulators.

Alibaba, the world’s biggest e-commerce company by total sales volume, and another company were fined in mid-December for failing to apply for official approval before proceeding with some acquisitions.