US-Facebook, Instagram, and WhatsApp, platforms both owned by Facebook, were all hit by a glitch on Wednesday that made it difficult for users to upload or view photos, with the cause of the problem not immediately clear.

Facebook tweeted that “we’re aware that some people are having trouble uploading or sending images, videos and other files on our apps. We’re sorry for the trouble and are working to get things back to normal as quickly as possible.”

Instagram, a platform that Facebook bought in 2012, tweeted a similar explanation, writing “We’re aware that some people are having trouble uploading or sending images and videos on Instagram.” It issued the same apology as Facebook.

Users of texting app WhatsApp, acquired by Facebook in 2014, also reported difficulty in uploading and viewing photos.

The photo problems for all three social platforms highlighted the centralization of major worldwide apps.

By contrast, Twitter, separately owned and run, did not report any problems as of Wednesday morning. Spokespersons for Facebook and Instagram did not immediately respond to request for comment on what was causing the glitch.

According to a Facebook outage map, Europe, the United States, and Brazil reported the highest level of problems using the platform. An outage map for Instagram found the problems concentrated in the same areas, with the biggest spike in the northeast states of the U.S.. WhatsApp’s problems mostly hit in Europe, Brazil, India, and Venezuela, where the app is used widely for texting.

The glitch came after a rough week for international networks, with millions of websites worldwide temporarily unable to load on Tuesday morning due to a massive spike in processor usage at internet provider Cloudflare.