Facebook’s week just went from bad to worse.

Facebook (FB), Instagram and WhatsApp all suffered outages midday Monday, according to public statements from the three Facebook services.

“We’re aware that some people are having trouble accessing our apps and products,” Facebook said on Twitter. “We’re working to get things back to normal as quickly as possible, and we apologize for any inconvenience.”

Outage tracking site Down Detector logged tens of thousands of reports for each of the services. Facebook’s own site would not load at all for about an hour on Monday; Instagram and WhatsApp were accessible, but could not load new content or send messages.

The reason for the outage was not immediately clear. However, multiple security experts pointed to a Domain Name System problem as a possible culprit. A spokesperson for the company did not immediately respond to a request for comment from CNN Business.

The outage came the morning after “60 Minutes” aired a segment in which Facebook whistleblower Frances Haugen claimed the company is aware of how its platforms are used to spread hate, violence and misinformation, and that Facebook has tried to hide that evidence. Facebook has pushed back on those claims.

The interview followed weeks of reporting about and criticism of Facebook after Haugen released thousands of pages of internal documents to regulators and the Wall Street Journal. Haugen is set to testify before a Senate subcommittee on Tuesday.

Shares of Facebook were down more than 5% in midday trading Monday, putting it on pace for its worst trading day in nearly a year.