USCIS - Direct Filing Addresses for Form I-140, Immigrant ...
For New I-140/I-907 Filings: ... have already filed Form I-140, and you wish to ... If your Form I-140 is pending with the Nebraska Service Center or the Texas ...
http://www.uscis.gov/portal/site/uscis/menuitem.5af9bb95919f35e66f614176543f6d1a/?vgnextoid=c31c5cdc2c463110VgnVCM1000004718190aRCRD&vgnextchannel=fe529c7755cb9010VgnVCM10000045f3d6a1RCRD