The 34-year-old Pantani, who won the Tour de France in 1998, was found dead in a hotel suite in the beachside resort city of Rimini on February 14, 10 years ago, and the court later ruled he had died accidentally of acute cocaine poisoning.
Tonina Pantani, the rider's mother, has always said she believed her son was murdered. Through her lawyer, Antonio De Rensis, she presented a report to the court that says Pantani was beaten and then forced to drink a lethal dose of cocaine dissolved in liquid, Italian media reported yesterday.
On her Facebook page, Tonina said the Rimini court had opened a murder investigation into her son's death.
Rimini lead prosecutor Paolo Giovagnoli confirmed that a murder inquiry against unknown perpetrators had been opened on the basis of the Pantani family's report.
"It is our duty to open an investigation," said Giovagnoli. "Pantani's mother has presented an expose, and we are studying it. We will investigate."
In Italy, an investigation must be opened by law if a crime is reported. Neither the Pantani family lawyer De Rensis nor prosecutor Giovagnoli immediately responded to calls to their offices yesterday.
"I will never stop until I see the truth written about Marco," Tonina Pantani told la Repubblica newspaper. "They murdered him, and I've always known it went this way."
"My sensation from the very beginning was that he had discovered something and somebody shut his mouth," she said, without elaborating further on a possible motive.
According to Pantani family claims, the cuts and contusions found on his body showed he had been beaten, and the high amount of cocaine found in his system could have only been reached if he swallowed the drug, something they say he would not have done willingly.
Pantani was nicknamed the "pirate" because he always wore an earring and a bandana over his shaved head, and he was a fan favourite because of his aggressive attacks during races, especially during steep climbs in the mountains. He became a leading sporting figure in 1998, winning both the Tour de France and Giro d'Italia in the same year.
This year, for the first time since Pantani's victory 16 years ago, an Italian, Vincenzo Nibali, won the Tour de France.