What are the standard icons for errors and warnings?

I'm looking for two types of icons. I want an icon that displays an error (action required), and an icon that displays a warning (watch out).

Now when I search for these icons I get a bunch of different results. For example exclamation marks in circles, squares, triangles etc. or an X in the same shapes.

I'm curious if it was ever 'officially' decided by a big UX authority what the standard look for those icons should be.