Oprah Winfrey did something that got her in trouble with the Nielsen TV ratings service over the weekend, according to The Hollywood Reporter. The trouble started when Winfrey sent out a tweet asking her fans to watch "Oprah’s Next Chapter," which aired Sunday.

Winfrey tweeted: "Every 1 who can please turn to OWN especially if u have a Nielsen box." The message violated Nielsen’s rules by mentioning she wanted to reach people with the company’s electronic boxes, which are used to measure ratings, the story says.

It was not clear what action Nielsen would take as a result. Nielsen said it was reviewing the incident and "may withhold, break out and/or make a note in the ratings," the story adds. Nielsen told The New York Times it would add an asterisk to OWN’s ratings noting “a possible biasing effect,” according to THR.

Winfrey’s representative immediately issued the following statement: “I removed the tweet at the request of Nielsen. I intended no harm and apologize for the reference. — Oprah Winfrey.”

About 25,000 of the more than 100 million U.S. TV homes have the Nielsen boxes, the story notes.