They are working to establish whether the sporting great was treated with negligence prior to his death at the age of 60.
His daughters have reportedly demanded to know what medication their father was taking.
On Sunday, several officers were seen stationed outside the house of neurologist Dr Leopoldo Luque in Buenos Aires.
Afterwards, Dr Luque told reporters that he had given investigators all records of his treatment of the footballer, as well as computers, hard drives and mobile phones.
Growing tearful, he defended his treatment of the troubled star, who died on Wednesday.
“I know what I did. I know how I did it…. I am absolutely sure that I did the best for Diego, the best I could,” he said.
The doctor added that he was not Maradona’s chief physician, but part of a medical team.
Diego Maradona – The Highs & Lows
It followed a public vigil at the country’s presidential palace where tens of thousands of weeping fans lined up to file past his coffin.
Maradona died in a house outside the Argentinian capital where he had been recovering from a brain operation on November 3.
He had suffered from a long series of medical issues, some related to overindulgence in drugs and alcohol. He was reportedly near death in 2000 and 2004.
Dr Luque described the former sportsman as a difficult patient, revealing that he had kicked the doctor out out of his house several times.
“Diego did what he wanted,” Dr Luque said. “Diego needed help. There was no way of getting through to him.”