(Reuters) - Shares of Facebook Inc rose as much as 4.2 percent on Thursday after Chief Executive Officer Mark Zuckerberg said the social network had not seen any meaningful impact on usage or ad sales in the wake of a data privacy scandal.

FILE PHOTO: Facebook CEO Mark Zuckerberg speaks on stage during the Facebook F8 conference in San Francisco, California, U.S., April 12, 2016. REUTERS/Stephen Lam/File Photo

The company’s shares have sunk 16 percent, wiping more than $80 billion from its market value since March 16, when the New York Times and London’s Observer newspaper broke news of the use of its data by political consultancy Cambridge Analytica.

Some investors see the chaos as a chance to snap up shares in a service for which there is scarce alternative, despite rising public scrutiny and the prospect of a grilling from U.S. legislators when Zuckerberg testifies before Congress next week.

Canada’s province of British Columbia and Canada’s federal government combined investigations on Thursday, saying they had launched a joint probe into Facebook and Canadian data firm AggregateIQ, while Australian authorities said they were exploring whether the social media company had breached user privacy laws.

The California State Teachers’ Retirement System, with nearly $1 billion in Facebook stock as of last year, on Thursday also said it would question the company about privacy protections.

Despite the probes and celebrities including singer Cher, actor Will Ferrell and Tesla Chief Elon Musk deleting their accounts, Facebook’s social app downloads improved on a monthly basis both in the United States and globally, according to Evercore ISI.

Facebook expanded its share of social app downloads in March by 33.2 percent from 30.1 percent, Evercore data showed.

Several Wall Street analysts said the stock’s decline presented a good opportunity

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