NEW YORK >> Twitter users were unable to access the micro-blogging service for about an hour today. 

Twitter said on its status blog that its engineers were investigating the issue. About an hour later, it said the issue had been resolved, and the short messaging service was working again. The company declined to say how widespread the outage was or what caused it.

Outages were once a relatively common occurrence for Twitter, but that was several years ago when it was new and trying to manage growth. It was shut down at least twice in August 2009, once for several hours, when hackers hobbled the site in a “denial of service” attack. 

There was no indication today that the outage was the result of malicious attacks.