Twitter logo is displayed at the entrance of Twitter headquarters in San Francisco on March 11, 2011 in California. (KIMIHIRO HOSHINO/AFP/GETTY IMAGES)

Twitter confirmed that some users were unable to access the service Thursday, marking the second time this month that the micro-blogging service has been hit with an outage.

The company said on its status blog that it was working to resolve the issue. Compuware’s Outage Analyzer tool indicated that users across North America and Europe may have been affected by the problem, but it’s not clear how many of the site’s estimated 200 million active users were unable to reach the service.

In its early days, Twitter used to have more frequent outages, making its iconic “fail whale,” which indicates the site is overloaded, a common online sight. As it has grown, the service has worked to stabilize its network, and outages are less frequent.

But the site can still show signs of strain during major events, as was clear earlier this month on Inauguration Day, when many were unable to send messages or visit the site. The company’s last widespread outage was in July, when the site was inaccessible for at least two hours. The company said that July’s outage happened when two parallel systems designed to back each other up coincidentally failed at the same time.

When reached for comment on the outage, spokeswoman Carolyn Penner pointed to the company’s post and said Twitter will be updating it as it gets more information.

According to a report from ABC News, some users also had problems accessing the Twitter-owned video service Vine on Thursday.

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