Thousands of city apartments are once again rent-regulated after state authorities they say were improperly deregulated.

Officials say 50,000 improperly deregulated apartments have been restored as rent-controlled.

More than $2 million will also be refunded to tenants who were overcharged in the last four years.

In 2012, the state's Tenant Protection Unit began tracking down apartments that had disappeared from the Office of Rent Administration's data.

The agency says they began monitoring rent at the apartments after notifying owners who failed to register rent-controlled units.

They also used the data to identify rent overcharges tenants were unaware of, which involved improvements that were never completed or weren't documented.