Shares of grocery delivery service Instacart dropped 11% in extended trading on Wednesday, following a report that said the U.S. Federal Trade Commission has begun an investigation into the company’s pricing practices.

The FTC sent a civil investigative demand to Instacart, Reuters reported, citing unnamed people.

A study released last week showed that prices for the same products in the same supermarkets that work with Instacart can vary by around 7%, which can result in over $1,000 in extra annual costs. Instacart responded that retailers determine prices listed in the app.

The FTC and Instacart did not immediately respond to requests for comment.

This is breaking news. Please refresh for updates.