Empowered by a recently enacted state law, the New York City government is stepping up enforcement on so-called “zombie properties,” vacant homes that are underwater on their mortgages, and has filed lawsuits against lenders holding onto five such properties in Brooklyn.

The city filed suit against Wells Fargo, CitiMortgage and three other lenders, which each hold one foreclosed property in Brooklyn, for more than $1 million in penalties for vacant properties where city inspectors found multiple code violations.