BRUSSELS (Bloomberg News) — European Union data protection regulators said on Wednesday that they would investigate Facebook over a feature that uses face-recognition software to suggest people’s names to tag in pictures without their permission, and a privacy group in the United States said that it planned to file a complaint with the Federal Trade Commission over the feature.

A group of privacy watchdogs drawn from the European bloc’s 27 nations will study the measure for possible rule violations, said Gérard Lommel, a Luxembourg member of the so-called Article 29 Data Protection Working Party. Authorities in Britain and Ireland said they are also looking into the photo-tagging function on the world’s most popular social networking service.

“Tags of people on pictures should only happen based on people’s prior consent and it can’t be activated by default,” said Mr. Lommel. Such automatic tagging suggestions “can bear a lot of risks for users” and the European data protection officials will “clarify to Facebook that this can’t happen like this.”

Facebook said on its blog on Tuesday that “Tag Suggestions” was available in most countries after being phased in over several months. When Facebook users add photos to their pages, the feature uses facial-recognition software to suggest names of people in the photos to tag based on pictures in which they have already been identified. Before the feature was introduced, users could tag pictures manually without permission from their friends.