Dec 27 (Reuters) - Britain’s competition watchdog said on Friday it would undertake an in-depth investigation into Amazon.com Inc’s purchase of a stake in online food delivery group Deliveroo, weeks after expressing concerns over the deal.

The Competition and Markets Authority said it had moved the probe to Phase 2 as both Amazon and Deliveroo had not cleared the doubts it had raised earlier this month before its Dec. 18 deadline. [bit.ly/2EY4Ete ] (Reporting by Pushkala Aripaka in Bengaluru; Editing by Anil D'Silva)