A message purporting to be from Blade Runner Oscar Pistorius to his fans thanking them for their support was a fake, the Olympian's family said.
The athlete, released on bail yesterday after being charged with premeditated murder over the Valentine's Day death of his girlfriend Reeva Steenkamp, has not issued any public comments.
It was thought that a message on his elder brother Carl's Twitter account was penned by the double amputee, but a spokeswoman later said this was not the case and that the account had been hacked.
Olympic athlete, Oscar Pistorius in Pretoria, South Africa, for his bail hearing charged with the shooting death of his girlfriend, Reeva Steenkamp
The message, thanking "every person that has prayed for both families" and signed by "Osca" was posted using the @carlpistorius handle.
Pistorius family spokeswoman Janine Hills said: "Carl did not tweet this afternoon, out of respect to Oscar and Reeva. We are busy cancelling all the social media sites for both Oscar's brother and his sister."
As of this evening, Carl Pistorius's Twitter account had been taken down while those belonging to his brother and sister Aimee remained.
Paralympic athlete Pistorius, known as the "Blade Runner", was granted bail following a four-day hearing in Pretoria, South Africa, a week after he shot Steenkamp dead at his home.
Following the hearing, he was seen arriving at his uncle Arnold's home.
He claims that when he fired shots through his bathroom door, he believed he was shooting at an intruder.
Prosecutors say Pistorius intended to kill the model however.
A funeral service for the 29-year-old law graduate took place last week.
The father of Ms Steenkamp has warned the 26-year-old athlete will have to "live with his conscience" if he is lying about how he killed her.
Barry Steenkamp said the Paralympian will "suffer alone" if his claim that he shot Ms Steenkamp accidentally, believing her to be a burglar, is false.
But Mr Steenkamp told the Afrikaans-language Beeld newspaper he might be able to forgive Pistorius one day if the double-amputee is telling the truth.
Mike Steenkamp, Ms Steenkamp's uncle, said Pistorius's family did not initially try to contact the bereaved parents but had since done so, in what he considered to be a poorly-timed approach.
Describing the mood of the Pistorius family after the bail decision was announced in court, he said: "Everybody wants to jump up with joy. I think it was just done in the wrong context, completely."
Olympic athlete, Oscar Pistorius , in court in Pretoria, South Africa, for his bail hearing
Beeld also quoted Ms Steenkamp's mother June as saying the family had received a bouquet of flowers and a card from the Pistorius family.
She said: "Yes, but what does it mean? Nothing."
Pistorius could be training again as early as Monday but his coach Ampie Louw said he will not be competing.
Arnold Pistorius has said the family is "relieved" that the athlete was granted bail, but added that they were also mourning the death of Ms Steenkamp.
"As the family, we know Oscar's version of what happened that tragic night and we know that that is the truth and that will prevail in the coming court case," he added.
The next hearing for Pistorius, whose bail was fixed at one million rand (£73,822) has been set for June 4.