Popular smartphone apps including Spotify and Pinterest suffered outages Friday due to an apparent bug in Facebook's systems.
"We are aware and investigating an increase in errors on the iOS SDK which is causing some apps to crash," Facebook posted on its developer site.
App users began reporting early Friday morning on Twitter that they were unable to open Spotify and other sites.
The site Downdetector, which monitors for internet problems in real time, showed a rise in problems for a number of applications, including Spotify, Pinterest, Waze and The New York Times.
It reported a major spike in problems around 1030 GMT and declining at around 1300 GMT.