One day after British authorities announced an investigation into a Facebook study that aimed to manipulate the emotions of 700,000 users, the company’s second-in-command, Sheryl Sandberg, offered a measured apology for the controversial experiment.

“It was poorly communicated,” Sandberg said, speaking in New Delhi on her Lean In campaign. “And for that communication we apologize. We never meant to upset you.”

While Sandberg notably failed to apologize for the experiment itself, Facebook will now likely have to answer to British regulators, who are currently probing whether any British citizens were involved in the study, and whether the anonymity of the pool was maintained, reports USA Today.

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The U.K. Information Commissioner’s Office (ICO) is working in conjunction with the Irish Data Protection Commissioner -- where Facebook’s European outfit is headquartered, Bloomberg reports.

“It’s clear that people were upset by this study and we take responsibility for it,” Facebook said in a statement to Entrepreneur.com. “We want to do better in the future and are improving our process based on this feedback. The study was done with appropriate protections for people’s information and we are happy to answer any questions regulators may have.”

Conducted in 2012, the experiment sought to address “the common worry that seeing friends post positive content leads to people feeling negative or left out,” explained its author, Adam Kramer. Unbeknownst to 700,000 users, the company tweaked feeds to emphasize positive or negative content, ultimately leading to widespread outcry when the study was published last weekend.

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