Whole Foods Market made a surprise move that caught its loyal customers off-guard.

Whole Foods sent an email to all the members of their loyal program saying they will no longer continue with their rewards program and digital coupons which officially takes effect on May 2.

The company said all their loyalty program will be integrated in the future to the Amazon Prime rewards promo.

Analysts led by Christopher Mandeville said the move could have been triggered after Amazon.com Inc. AMZN, -1.89% acquired Whole Foods Market in June 2017.

Mandeville said the latest move of Whole Foods could have a major impact among grocers since it could heighten competitive pressures for all grocers.

Sources said since acquiring Whole Foods, Amazon already implemented some changes such as price cuts on certain items and 5% cash back on purchases made at Whole Foods using the Prime Rewards Visa V, +0.19% card.