LONDON, Sept 7 (Reuters) - Britain's competition regulator on Monday fined Amazon 55,000 pounds ($72,364) after the U.S. online giant delayed an investigation into its purchase of a 16% stake in food platform Deliveroo by failing to provide documents on time.

The Competition and Markets Authority (CMA) finally cleared Amazon's stake purchase in August - 16 months after the company led a $575 million fundraising in Deliveroo.

The regulator said 189 documents, which included a significant amount of information relevant to its Phase 2 Amazon/Deliveroo merger probe, were not produced until after the initial deadline.

"Although Amazon did ultimately provide all of the information required, the CMA considers that Amazon's behavior caused unnecessary delays to the CMA's investigation," it added.

($1 = 0.7601 pounds) (Reporting by James Davey, Editing by Paul Sandle)