The New York City Housing Authority has identified 6,000 additional apartments where children live who are at risk of lead exposure.

The announcement was made by the federal monitor. The number is three times more than originally identified two years ago.

NYCHA says the announcement is the result of its dialogue with residents during in-apartment X-ray fluorescence (XRF) testing visits and the housing authority's door-knocking campaign.

MORE: Statement released by NYCHA Federal Monitor Bart M. Schwartz

The federal monitor says they must make sure children in those apartments are protected from lead risks and that NYCHA has already undertaken numerous steps in that direction.

A Vision Zero campaign was announced by Mayor Bill de Blasio two years ago to eradicate lead paint poisoning. On Thursday, the mayor said that they are on the clearest path yet to making it happen.

"It can be done. It must be done. We're seeing many, many fewer cases,” he said. “We put out the information quarterly and there's been a steady decrease, but if there's anything we got to double back and go farther, we will."

The mayor also says they will follow up on this federal monitor report and act immediately.

NYCHA released a statement saying, “NYCHA is aggressively working to identify apartments where there are children under 6 years old, and our monumental efforts to overhaul our lead program have resulted in the nation’s most comprehensive assessment of public housing apartments presumed to have lead-based paint. We are inspecting and remediating every day, and will continue to make apartments with children under six our chief priority.”