Jessica Guynn

USA TODAY

SAN FRANCISCO -- Facebook's No. 2 executive Sheryl Sandberg apologized on Wednesday for the psychological experiment the giant social network conducted on nearly 700,000 unsuspecting users.

She said the experiment which tested whether Facebook could manipulate users' emotions was "poorly communicated."

Sandberg made the comments while on a visit to New Delhi, according to the Wall Street Journal.

Sandberg is in India meeting with businesses that advertise on Facebook to generate more revenue from emerging markets.

Her apology came as British data protection authorities said Wednesday that they are investigating the Facebook experiment. They are working with authorities in Ireland, headquarters of Facebook's European operations. French authorities are also reviewing the experiment.

"This was part of ongoing research companies do to test different products, and that was what it was; it was poorly communicated," Facebook's chief operating officer said of the one-week experiment in 2012. "And for that communication we apologize. We never meant to upset you."

The research was published in the March issue of the Proceedings of National Academy of Sciences.