Question on Legal Obligation to Report Online Content

If you encounter suspected criminal activity on a social media platform (EX: identity theft, narcotic sale, abuse material, etc) are you legally required to report it to law enforcement directly? Or is reporting the post to the social media company who owns the platform sufficient to avoid legal liability?

In other words, is there a legal obligation for someone to report suspected criminal activity encountered on social media directly to law enforcement (such as reporting it to the FBI's tip line), or is it sufficient to just report the post to the social media platform's moderation team and let them pass the information off to law enforcement at their discretion (such as if I report an illegal post on Facebook)?