And one of the victim's sisters accused Sinn Fein on Tuesday of continuing to try to cover up the crime.
Sinn Fein is seen as the political wing of the Irish Republican Army (IRA).
Sinn Fein, which has already suspended seven members linked to the January slaying of Robert McCartney but identified none of them, admitted that one of the party's candidates for May's election to the Belfast City Council was in the bar.
It issued a statement from the candidate, 23-year-old Deirdre Hargey, in which she said she provided a statement to a lawyer, but offered no specifics.
On Saturday, Sinn Fein said a candidate in Northern Ireland's 2003 legislative elections, Cora Groogan, 23, was also in the bar. Groogan issued a statement saying she heard a commotion but saw nothing.
The IRA has admitted that two of its members slashed McCartney's neck and stomach after he intervened in a dispute at the pub on 30 January. The 33-year-old man died hours later.
A campaign by McCartney's five sisters to have his killers brought to justice has focused attention on the outlawed IRA's continued grip on Catholic parts of Belfast, where telling police about its activities can result in a beating or even death.
Catherine McCartney, one of the sisters, accused Sinn Fein of continually trying to conceal and downplay their members' role in the attack.
"I find it hard to believe that we've been campaigning for six weeks and still not a single person has been charged with Robert's murder," she said in an interview in her sister Paula's home in Short Strand.
"I find it hard to believe that we've been campaigning for six weeks and still not a single person has been charged with Robert's murder"
Catherine McCartney, sister
of slain Robert McCartney
She said the neighbourhood's IRA head, who allegedly ordered his men to attack her brother, was seen buying food and a newspaper at a local Short Strand shop last weekend. The man who actually knifed her brother to death, she said, was spotted in local pubs.
"Everybody knows who killed my brother, and who ordered it, but they're still strutting about the place like they own it," she said.
Sinn Fein involvement?
She said Sinn Fein made the latest admissions on its members' presence at the pub only because the family received information from taxi drivers, who picked up the Sinn Fein activists outside the pub.
She said the party initially claimed that Groogan left the pub two hours before the attack, then admitted she was there until 11 pm - when McCartney was already lying fatally wounded in a street beside the bar.
"The fact is, Sinn Fein keeps saying they want people to give evidence. But here we have two examples where Sinn Fein people are playing deaf, dumb and blind," the sister said.
Paula McCartney stressed that the family included long-time supporters of Sinn Fein and the IRA, but were disgusted by the movement's determination to protect its own at the expense of justice.
"He seemed genuine when he met us, when we thought the problem was just a matter of IRA intimidation. Now we know better. It's clear that Sinn Fein is heavily into the cover-up"
Catherine McCartney, on Sinn Fein leader Gerry Adams
All five McCartney sisters and their brother's fiancee, Bridgeen Hagans, are scheduled to meet US President George Bush at a St Patrick's Day reception at the White House on Thursday.
Sinn Fein leader Gerry Adams, who has been part of the White House celebration for years, has been barred from official US government functions this year.
On Wednesday, McCartney's sisters are scheduled to meet Bush's envoy to Northern Ireland, Mitchell Reiss.
They are also expected at some social functions to bump into Adams - who met the McCartneys last month and reassured them he would press for witnesses to come forward. But Catherine McCartney said she probably would not shake his hand.
"He seemed genuine when he met us, when we thought the problem was just a matter of IRA intimidation," she said. "Now we know better. It's clear that Sinn Fein is heavily into the cover-up."