Twitter went down for several hours on Thursday afternoon, depriving users of a place to complain that Twitter was down.

The Twitter outage began at 11:59 a.m. ET, according to Twitter's page on tracking site Pingdom. Service returned intermittently around 1 p.m., but less than an hour later, Twitter crashed again.

"Engineers are currently working to resolve the issue," a Twitter spokeswoman told CNNMoney.

Twitter updated its status blog at 1:42 saying "the issue has been resolved and all services are currently operational" -- but at 2:16, another update from Twitter backtracked and said "the issue is on-going."

An hour later, Twitter seemed to be working for most users. Shortly after 3 p.m. ET, Twitter's PR account tweeted that the issue was caused by "a cascaded bug in one of our infrastructure components."

That explanation came after a hacker group, UGNazi, claimed to several media outlets that it had taken Twitter down in a distributed denial-of-service (DDoS) attack.

The June 21 Twitter outage was the longest service disruption since an hour-long episode on October 7, which came during a month filled with hundreds of very brief outages, according to Pingdom's data.