Encrypted instant messaging app Signal was hit by an outage late Sunday that interrupted services on the platform.
"Signal is currently down, due to a hosting outage affecting parts of our service," the company said on Twitter. "We're working on bringing it back up."
Internet outage monitor DownDetector said users began reporting network problems at 11:05 pm Eastern Standard Time (0305 GMT).
The site logged reports of interrupted service in the United States, Europe, Hong Kong and other parts of the world.
First launched in 2014, Signal saw a surge in downloads earlier this year after Facebook-owned messaging service WhatsApp tweaked its terms of service and sparked privacy concerns.
Its profile was boosted by a tweeted recommendation by tech entrepreneur and Tesla founder Elon Musk and the app was downloaded more than 100 million times as of March.