The U.S. Justice Department said on Wednesday it has opened a civil investigation into the health and safety conditions in New York City's public housing and the extent residents have elevated blood-lead levels.

In a court filing, the office of Manhattan U.S. Attorney Preet Bharara asked a federal judge to direct the city's Department of Health and Mental Hygiene to produce information in response to a civil investigative demand.

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The filing said the investigation was also looking at whether the New York City Housing Authority (NYCHA) had made false claims to the U.S. government related to conditions in its public housing.

Nick Paolucci, a spokesman for the city's law department, said the Department of Health is cooperating in the investigation. A spokeswoman for NYCHA had no immediate comment.

Lead is a toxic agent that can damage the nervous system. Public attention over lead poisoning has grown in the wake of the water contamination crisis in Flint, Michigan.

More than 400,000 people reside in the New York City Housing Authority's 328 public housing developments, according to its website.

The court filing on Wednesday by Bharara's office related to an investigation into possible violations of the False Claims Act.

The investigation, which dated back to at least November, has also looked at the city's Department of Homeless Services, according to the filing.

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Beyond information about people with elevated blood-lead levels in NYCHA public housing, Bharara's office has sought "documents reflecting complaints of unsafe, unsanitary, or unhealthful conditions," the filing said.

Some of the records sought include notification letters and lead-based paint evaluation results, according to the filing.

The health department has agreed to produce the information but required a court order to legally do so, lawyers in Bharara's office wrote in a letter seeking an order from U.S. District Judge Deborah Batts.