Gmail is getting more persistent advertisements that have started popping up in the middle of some users’ inboxes, as first reported by 9to5Google. Several screenshots posted to Twitter show promotional messages mixed in with actual emails on Gmail’s desktop site, and users aren’t very happy about it.

While Gmail has long placed ads at the very top of the Promotions and Social inboxes, it never dared to stick them in between messages. The new placement makes it even more confusing to distinguish between actual emails and ads, even if the promotions have the little green “Ad” icon placed next to them. It’s not clear if this is some kind of test or a gradual rollout. (I’m not seeing ads scattered within any of my inboxes just yet.)

Additionally, in recent weeks, some users on the client’s mobile app have also started noticing ads with obnoxious, full-size images at the top of their inboxes.

In a statement to The Verge, Google spokesperson Rachael King confirmed that Gmail first launched ads in between messages in the Promotions tab on mobile last year, but notes that the company has since brought them to the desktop version of Gmail as well.

“We are always experimenting with formats and working on ways to help people discover and connect with new businesses,” King says. “The Promotions tab shows promotional emails from businesses that people subscribe to, as well as offers and deals from companies people might like. We rolled out instream ads in the Promotions tab last year across mobile and in the past month expanded to desktop as well.”

Google’s website currently doesn’t indicate whether it sells ads placed smack-dab in the middle of inboxes, with one support page saying that Gmail offers “expandable ads at the top of people’s tabs.” Another page about Google’s Discovery campaigns shows an example of a Gmail ad that, once again, appears at the top of a user’s inbox.

In response to one user’s concerns about the middle-of-the-inbox ad placements on Twitter, the official Gmail account vaguely said that “doesn’t sound good” and directed them to a support page that explain how ads work.

Update May 8th, 5:10PM ET: Updated to add a statement from a Google spokesperson.