Slack's outage grew in severity Monday morning, as its services remained down for many users hours after initial disruption began.

Issues began to bubble up around 10 a.m. EST, according to Downdetector, which tracks such problems. Users were unable to send messages or load channels. The outages came as many in the U.S. and elsewhere returned to work after the holiday break, ironic timing that was not lost on customers.

Slack initially described the problem as an "incident" and said its teams were "aware" and "investigating the issue," a spokesperson told Protocol. The company then updated its statement to "reflect an outage in service," but declined to provide an underlying reason for the problems. Anecdotally, the service appeared to be recovering at around 12:30 p.m. EST.

It's not uncommon for providers to report short-term glitches in services. Google, for example, encountered issues in December that took Gmail and other products offline for roughly 45 minutes.