The page at https://example.com was loaded over HTTPS, but requested an insecure image http://example.com

I see this error on my site while loading in Chrome. But it does not mention which specific image it is looking for

The page at https://example.com was loaded over HTTPS, but requested an insecure image http://example.com

Can I have some suggestions how to find what is loaded on HTTP. I tried various plugins on Chrome, but none of them were able to figure out the HTTP URL.