SAN FRANCISCO - Twitter is investigating a problem that affected service to its users in the United States, Canada and Europe for more than an hour Thursday.

The disruption began about 2:46 p.m Eastern Time, according to DownDetector.com, a site that monitors outages on social media.

Twitter Canada’s spokesman confirmed the social media service was still down about an hour later, shortly before service was restored.

Outages were widespread in Twitter’s early years, so much so that a cartoon “fail whale” the company would put up during outages came to symbolize Twitter almost as much as its little blue bird icon.

The whale was retired in 2013, largely because Twitter no longer wanted to be associated with what it represented. Outages have become far less common since then.

The outage occurred as President Donald Trump — an avid Twitter user — convened a White House conference of critics of Big Tech.