An investigation has been launched after a man died in hospital an hour after a woman allegedly sabotaged its gas supplies.

The 72-year-old died at Sutherland Hospital, in Sydney's south, about 2.30am on Tuesday, police confirmed on Wednesday morning.

About an hour earlier, a 42-year-old woman allegedly shut off the public hospital's medical gasses, forcing the facility to switch to portable oxygen and air for two hours.

Just after midnight she also allegedly cut the gas and water mains at the nearby Kareena Private Hospital at Caringbah before setting off the fire hoses.

She is due to appear in court on Wednesday on charges of destroying or damaging property and custody of a knife in a public place.

A report on the man's death is being prepared for the coroner.

On Tuesday, the NSW g

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