The UK's foremost privacy and data watchdog has said it will be investigating Facebook following the revelation earlier this week that the social network had conducted a study in which it fiddled with users' News Feeds in order to see if it could manipulate their emotions.

Facebook has come under fire for the secret experiment because of its psychological nature, which did in fact prove to be unnervingly effective at controlling people's emotional reactions. The Information Commissioner's Office (ICO) has said that it will review the situation thoroughly in order to try to establish whether Facebook has broken UK data protection law.

"We're aware of this issue, and will be speaking to Facebook, as well as liaising with the Irish data protection authority, to learn more about the circumstances," a spokesman from the ICO told Wired.co.uk.

Facebook's European headquarters are based in Dublin, which is why it will be taking up the issues with the authorities in Ireland. It's likely that the regulator will look into whether users gave their consent for their data to be used in such a way. Informed consent is something that has been at the very center of the argument. Making sure study subjects have given their permission and know what they have signed up to, or informing them at the very earliest stage possible, is considered to be an ethical responsibility of psychologists performing experiments, according to guidelines issued by the British Psychological Society.

The ICO will also no doubt look at exactly which data and how much of it was used in the experiment. It's not clear how many British Facebook users were involved in the experiment—all we know is that 689,000 members of the social network (including those under the age of 18) with their language set to English were unwitting participants in the study. It emerged yesterday that Facebook added the information about user data being exploited for research to its user agreement several months after it performed the experiment.

Facebook has apologized for upsetting users, and, according to the Financial Times, its European director of policy has said the social network will be happy to answer any queries from regulators.

This story originally appeared on Wired UK.