Twitter Inc. suffered an apparent worldwide outage on Thursday that lasted about an hour and a half, affecting users of its social network from New York to Sydney. Some service was restored and tweets began appearing again at about 7 p.m. New York time.

The company earlier said it saw no evidence of a security breach or hack, but was investigating internal causes for the problems. San Francisco-based Twitter had said on its status website it was looking into an “irregularity” with its APIs, the technology that lets different software systems interact with each other.

Downdetector.com, which tracks outages, received at least 50,000 reports about problems with the social media platform, starting at about 5:15 pm. The number of Twitter reports on the site had declined to less than 6,000 as of 7:03 p.m.