For some on Facebook, what’s old was new again on Friday.

Users reported that photos originally posted months ago reappeared on the site. In a statement Facebook said it was “aware and are currently investigating.”

Stephanie Milot, a reporter for PC Magazine, wrote that four of her photos were re-posted Friday. They apparently weren’t merely resurfacing in users’ newsfeeds; the old posts were marked with new dates and timestamps, suggesting they had been posted anew.

Several users have raised the issue on Facebook’s help forum. Some expressed concerns that their accounts were being hacked.

“Tonight I have seen two posts on my page as new posts, but both are from 6 months ago, and are old posts. Why is this happening? Have I been hacked?” one user wrote shortly after 6 p.m.

Earlier, another user described the problem and asked: “Does this activity mean my account is vulnerable?”

The complaints came after Facebook told users Thursday that it has compiled videos for them that showed their “year in review,” essentially a video slideshow of individuals’ photos from 2016 that they can share with their friends.

The latest glitch on the social network comes one month after Facebook mistakenly said some of its 1.79 billion monthly users were dead.