Lobato, however, said some of the patients were awake and conscious moments before the drugs were administered.

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"There are nearly 300 more that we are looking into, " Dr Lobato said.

BBC: Brazil studies Curitiba doctor's link to 300 deaths

The documents show the authorities also investigated other public figures such as singer Roberto Carlos, TV show hosts Silvio Santos and Hebe Camargo and author Monteiro Lobato.

BBC: Records prove Pele was probed by Brazil military

In an interview with CNN affiliate TV Globo, Mario Lobato, the doctor tasked by the health ministry to investigate the case, said the number of deaths could be much higher.

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But the medical records of 1, 700 patients who died at the hospital in the last seven years are now being studied and more than 20 were now deemed suspicious, Dr Mario Lobato - the chief investigator assigned by Brazil's health ministry - told Globo.

BBC: Brazil studies Curitiba doctor's link to 300 deaths