Facebook chief Mark Zuckerberg has admitted to the United States Congress that his social media network did not do enough to prevent misuse of data, Reuters reported. He apologised after it came to be known that the data of 87 million Facebook users was harvested by the British political consulting firm, Cambridge Analytica.

“It’s clear now that we didn’t do enough to prevent these tools from being used for harm,” Zuckerberg said in a written testimony released by the US House Energy and Commerce Committee on Monday. Over the next two days, Zuckerberg is set to speak at congressional hearings where he will be asked how user data was compromised, and how ads and posts were placed by Russian operatives before the 2016 presidential election in the United States, The New York Times reported.

“We didn’t take a broad enough view of our responsibility, and that was a big mistake,” Zuckerberg said in his written remarks. “It was my mistake, and I’m sorry.”

“It’s not enough to just connect people, we have to make sure those connections are positive,” Zuckerberg plans to say in his testimony, according to The Washington Post. “It’s not enough to just give people a voice, we have to make sure people aren’t using it to hurt people or spread misinformation.”

The social media company has faced widespread criticism since it was revealed that it was aware that Cambridge Analytica had been harvesting the data of Facebook users for years.

The British data analytics firm was initially accused of using the information of 50 million Facebook users to bolster US President Donald Trump’s campaign before the 2016 election. But on April 4, the social media company said that the breach had impacted 37 million more people.