(Reuters) — Singapore’s competition watchdog said it had reasonable grounds to suspect competition had been infringed by Uber’s deal to sell its Southeast Asia operations to rival ride-hailing firm Grab.

In a rare move, the Competition Commission of Singapore (CCS) has commenced an investigation into the deal and proposed interim measures that will require Uber and Grab to maintain their pre-transaction independent pricing, the watchdog said in a statement on Friday.

It is the first time the commission has issued interim measures on any business in the country.

Uber and Grab announced the deal on Monday, marking the U.S. company’s second retreat from an Asian market.

Under the deal, Uber will take a 27.5 percent stake in Grab, which is valued at around $6 billion, and Uber CEO Dara Khosrowshahi will join the Singapore-based company’s board.

CCS proposals, effective immediately, also require both Grab and Uber not to obtain from each other any confidential information including pricing, customers and drivers.

The measures will be effective until the completion of its investigation.

The two firms will be given an opportunity to make written representations to the CCS upon receipt of the proposed interim measures, it said.

Singapore has a voluntary merger notification regime, and CCS has yet to receive the notification from Uber and Grab as of Friday, although the companies have indicated their intention to file a formal merger notification, CCS said.

Grab and Uber were not immediately available for comment.

(Reporting By Miyoung Kim, additional reporting by Fathin Ungku; Editing by Himani Sarkar)