Dear site owner or webmaster of http://www._____________________/, We've detected that some of your site's pages may be using techniques that are outside Google's Webmaster Guidelines. Specifically, look for possibly artificial or unnatural links pointing to your site that could be intended to manipulate PageRank. Examples of unnatural linking could include buying links to pass PageRank or participating in link schemes. We encourage you to make changes to your site so that it meets our quality guidelines. Once you've made these changes, please submit your site for reconsideration in Google's search results.
There is no link buying or link scheme participation is happening. Have been building some legit back links through warriors who are offering their services here. That has been stopped for couple of months now. May be that sudden stop has caused the issue? Or how can those unnatural links can be identified and removed?
Any advise would help. Thanks.