SAN FRANCISCO (AP) - Twitter says it is investigating a problem with its service . Users across the U.S. and elsewhere are not able to access Twitter.

  

The company is not saying how widespread the outage is. The disruption appears to be affecting both web-based and mobile users.

  

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 didn't want to be associated with what it represented any more. After all, outages had become far less common.

  

The outage is occurring as President Donald Trump convenes a White House conference of like-minded critics of Big Tech.