Twitter Inc. suffered downtime earlier today after introducing the ability for Twitter Blue subscribers in the U.S. to post tweets of up to 4,000 characters.

The additional feature was announced at 3 p.m. EST in an extended post on Twitter. Outside the ability to post up to 4,000 characters, normal Twitter restrictions apply. Twitter Blue users posting longer tweets on the web also can’t save them as drafts or schedule the longer tweets to be posted later.

Addressing concerns about how long tweets will affect timelines, Twitter said that only the first 280 characters will be shown on timelines, with a “show more” prompt available to read the whole tweet.

The announcement should have been the lead Twitter story of the day, complete with some backlash from users, but the company then went down. The first sign of trouble started with users in the U.S. and Canada receiving messages that they were “over the daily limit for sending Tweets.” From about 4:20 p.m. EST, other users started reporting that Twitter was down altogether, according to data from Downdetector.

Twitter users were still reporting issues as of 7 p.m. However, The Verge reported that access had mostly recovered from its technical issues earlier in the day, some issues with direct messages and TweetDeck aside.

The cause of the outage remains unknown, but leaked emails from Elon Musk to Twitter employees would suggest that it may have been an issue with data centers.

“Please pause for now on new feature development in favor of maximizing system stability and robustness, especially with the Super Bowl coming up,” Musk wrote in an initial email, adding in a follow-up email that employees “should also pause on transitioning away from Sacramento, consolidating Atlanta,” referring to Twitter data centers “and reducing [Google Cloud Platform] usage until at least next week.”

A Twitter employee told Fortune that the Slack channels of the Twitter engineering team were “going crazy” and that teams were still looking at various ideas around why the downtime and error message occurred, including recent changes to Twitter’s application programming interface to a data center issue.

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