Authorities initially said the Thursday attack at an auto dealership in the al-Bayaa neighbourhood killed at least 55 and wounded more than 60. The Islamic State group claimed credit for the bombing.
The officials spoke on condition of anonymity because they were not authorized to brief reporters.
IS, in a statement early Friday, said its fighters detonated bombs in a parked car among a gathering of Shiites in the Fifth Police district Thursday. It did not give further details.
The extremist group has carried out near-daily attacks in Baghdad despite suffering military setbacks elsewhere in the country, including in the northern city of Mosul, where U.S.-backed Iraqi forces have been waging a major operation since October.
The spiritual leader of Iraq's Shiites Grand Ayatollah Ali al-Sistani, expressed his condolences for the victims' families and called on those "responsible for decision-making to recognize their responsibility to preserve security."
His comments were delivered at Friday prayers by his representative, Ahmed al-Safi, in the holy city of Karbala.
The U.S. State Department condemned the bombing, saying such attacks show the extremist group's "utter contempt for human life and its efforts to sow discord and division among the Iraqi people."
Another four attacks in and around Baghdad on Thursday killed eight people and wounded around 30, authorities said.
The bomb attacks claimed by IS are seen as an attempt to distract attention as the militants cede territory along front lines in northern and western Iraq.
Also on Friday, followers of influential cleric Muqtada al-Sadr began gathering in Baghdad's downtown Tahrir square for a silent demonstration called by al-Sadr in a statement Thursday night.
The demonstration comes after last weekend's clashes with police that left five dead.
Al-Sadr is demanding an overhaul of the commission overseeing local elections scheduled this year. He has accused the commission of being riddled with corruption and has called for its overhaul
Security authorities Friday blocked roads leading to the square but there was no heavy security presence in the area.
FEATURED IMAGE CAPTION: Civillians are seen through a burned car at a used car dealer's parking lot in the southwestern al-Bayaa neighbourhood, Baghdad, Iraq on Friday, Feb. 17, 2017, a day after a car bomb. The car bomb claimed by the Islamic State group killed scores of people.