SAN FRANCISCO (AP) — Yelp says it will alert users if it suspects that a business has tried to buy fake, misleading reviews on its site.

Yelp Inc. said Thursday that some businesses go to ‘‘extreme lengths’’ to boost positive reviews. This includes paying people to write them.

While Yelp already filters suspected fake reviews, the alerts will add an extra layer of scrutiny. San Francisco-based Yelp says alerts will stay on a business’ page for 90 days after it’s placed there. If Yelp finds ongoing efforts to post fake reviews, the alert will remain longer.

Consumers can click on the alert to see more details on the misleading reviews, including screenshots.