Facebook had its longest outage since 2010 early Thursday morning, leaving millions of users worldwide unable to access the social network for about half an hour.

Starting at 4 a.m. ET, the site's outage incited panic among users as well as the hashtag #FacebookDown, USA TODAY reported.

The U.S., U.K., Ireland, Israel and India were affected as well as more countries across Asia and the Middle East.

A Facebook spokesman said the problem, which took out the site as well as the mobile version and Messenger app, stemmed from a system update.

"Late last night, we ran into an issue while updating the configuration of one of our software systems," said Facebook spokesman Jay Nancarrow, as quoted by USA TODAY. "Not long after we made the change, some people started to have trouble accessing Facebook. We quickly spotted and fixed the problem."

That half hour of downtime cost the world's biggest social network half a million dollars, a Forbes report estimated.

Since Facebook's first-quarter revenues of $2.5 billion divide to around $1.16 million per hour, the company likely lost around $500,000 in ad revenue during the outage, Forbes reported.

The site rarely experiences outages, but they have occurred several times during the last few years.

"Nothing is more important to us than making sure Facebook is there when people need it, and we apologize to anyone who may have had trouble connecting last night," Nancarrow said.

See Now: OnePlus 6: How Different Will It Be From OnePlus 5?