Google Alerts 20,000 websites they might be infected with malware

According the Google Search Quality team, they are concerned that the 20,000 site might be injected with a javascript redirect malware.
 -"Specifically, we think that JavaScript has been injected into your site by a third party and may be used to redirect users to malicious sites,"

The folks at Google are advising sites to search ( HTML, JavaScript or PHP files) their sites for  files containing "eval(function(p,a,c,k,e,r)" in particular.