Rome — A nursing home in Milan where nearly 200 residents have reportedly died of the new coronavirus is at the center of an investigation into suspected negligence by managers, Italian police revealed Friday.

Tax police seized documents this week in the offices of the Lombardy regional government in a probe centered on the Pio Albergo Trivulzio rest home in Milan where, according to Italian daily La Repubblica, 190 seniors have died since the start of the COVID-19 outbreak, although official numbers are not available.

The investigation also involves other care homes in Milan and across the region, where directors are suspected of culpable negligence.

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"We are working to fight the virus and protect Lombards," regional governor Attilio Fontana told Italian news agency ANSA, stressing that his office was offering "maximum collaboration" with investigators.

Health and hygiene police said they carried out inspections at 600 nursing homes across Italy this week, and found "irregularities" at 17% of the facilities. The police said 15 of the homes had to be closed down.

This month CBS News filed an exclusive report from inside a nursing home in Lombardy where doctors reported 33 COVID-19 deaths, but none of the deceased were tested for the disease nor included in Italy's official death toll.

Doctors there said they were unaware of any police investigation into their facility.

More than 22,000 people have died of the new disease in Italy, but many policymakers and doctors say that toll is likely a significant under-count due to insufficient testing for the disease, and under-reporting of deaths.

The Lombardy region accounts for more than half of all the recorded coronavirus deaths in the country.