The news led to several Italian media regurgitating the theory that 'Il Pirata' was murdered in 2004.
"We have just received documents sent by those close to (Pantani) and we have opened an investigation," said Paolo Giovagnoli, the public prosecutor in Rimini, where Pantani's body was found in a hotel room on Valentine's Day 2004.
"We will read them and if we decide to proceed with a new investigation we will appoint an examining magistrate to do so."
The 1998 Tour de France winner was initially recorded as having died of an acute cocaine overdose.
The news led sports daily La Gazzetta dello Sport to run the headline: "Pantani was killed, forced to drink cocaine."
The newspaper continued to claim that the investigation had been reopened into "homicide and tampering with a body and crime scene."
Pantani was 34 when he was found dead in room D5 of the 'Le Rose' hotel -- which was soon after dismantled -- in the seaside town of Rimini in the east of Italy, a town known for its problems with drug trafficking and the 'omerta' (voluntary silence) practised by its residents with regard to local crime.
Pantani's mother Tonina has long campaigned to have the death of her son requalified as murder and now she seems to have gained more widespread support.
La Repubblica newspaper claimed there had been a cover-up in the original investigation.
"On top of the real truth there has been laid, and perhaps cemented, a very much more convenient truth, that of an overdose," it said.
The newspaper went on to claim that Pantani's body had suffered "blows consistent with a brawl" and that the "body showed signs of having been moved".
It also said there was "a crazy amount of drugs in the body" as well as "a suspicious bottle of water", leading to the theory that Pantani had been forced to drink a lethal amount of cocaine mixed with water.
The original hypothesis of an overdose fitted well with the facts known at the time. After being kicked out of the 1999 Giro d'Italia after giving an adverse reading for his haematocrit level -- suggesting Pantani was taking the banned blood booster EPO, for which there was no test at the time -- the Italian became depressed and addicted to drugs.
He also faced a lawsuit for sporting fraud related to his blood values during the 1999 Giro, of which he was acquitted as doping was not considered a crime in 1999.
He was admitted to a psychiatric clinic in 2003 where he received treatment for drug addiction.
He never managed to rediscover his dominant form from 1998, when he won both the Tour and Giro, and slinked away from the sport in 2003.
The suggestions of murder are not new as French journalist Philippe Brunel claimed in a book published in 2007 about Pantani's life and death that the inquiry had settled too quickly on the hypothesis of a drugs overdose.
A recent report by professor Francesco Maria Avato, commissioned by the Pantani family, claimed that the "huge amount of drugs found in Pantani's body could only have been consumed in water".
He added that the amount discovered in Pantani's belly, around six times a lethal dose, would have "burnt the mouth and inflamed the stomach."
The report pointed to other anomalies such as the contents of Pantani's breakfast which had not been ordered at the hotel reception and included ice cream, despite there being no freezer in his room.
Avato said these elements could only be explained by someone "polluting" the crime scene and "violating every legal procedure".
Rebubblica concluded that the truth about what really happened to Pantani "is a story yet to be written".