The memo was sent after Di Maria received anonymous tip-offs about the practice at the hospital, the report said.
Social services chiefs have opened an internal inquiry into the affair and also referred it to the local prosecutor's office.
Director of social affairs Guido Scoditti said he had no choice but to pass the matter on to the authorities.
"The director of the hospital has certainly made an error, he should not have sent this memo, he should have informed me directly.
"The alleged consumption of cocaine in a hospital environment should certainly not be dealt with in this way," he said.
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Social services chiefs have opened an internal inquiry into the affair and also referred it to the local prosecutor's office.
Director of social affairs Guido Scoditti said he had no choice but to pass the matter on to the authorities.
"The director of the hospital has certainly made an error, he should not have sent this memo, he should have informed me directly.
"The alleged consumption of cocaine in a hospital environment should certainly not be dealt with in this way," he said.
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