The Philippine government said Friday it was investigating the breach of data of its citizens who use Facebook, after a massive leak of user information to British political consultancy Cambridge Analytica.

Manila’s National Privacy Commission has written to Mark Zuckerberg requiring the Facebook chief to submit to the government body documents that would shed light on the scope and impact of the leak on Filipino users.

“We are launching an investigation into Facebook to determine whether there is unauthorized processing of personal data of Filipinos,” said a copy of the letter, released to the press Friday.

The letter, dated Wednesday, said 1.18 million Filipino Facebook users “may have been affected by the Cambridge Analytica incident.”

“The Philippines has exceeded user growth projections and now has more than 67 million active Facebook users. It is our duty to protect the data privacy interests of these users, and to provide those affected with avenues for redress,” the letter added.

The Facebook founder apologized in US congressional hearings this week over how his company has handled the growing furor over online privacy.

Zuckerberg said Facebook had “failed” to protect people’s information following the use by Cambridge Analytica of data scraped from 87 million Facebook users to target political ads ahead of the 2016 US presidential election.

Separately, Philippine President Rodrigo Duterte Friday rejected suggestions in the local press that his election campaign team worked with Cambridge Analytica in his successful 2016 presidential run.

“I don’t know them. Honestly, I don’t believe in surveys,” he told a news conference in his southern home city of Davao.

“And why would I pay these fools from Cambridge to work for my campaign? I might have lost with them,” he added.

The local press this week published a photograph supposedly showing Duterte election campaign officials sharing a meal with the Cambridge Analytica chief executive in 2015, a year before the presidential election.