The so-called Islamic State (IS) has claimed responsibility for the massacre at a gay nightclub in Orlando, but US officials said they had seen no immediate evidence linking the militant group to the worst mass shooting in America's history.
The claim from IS was carried by Amaq, the organisation's news agency.
The armed attack that targeted a gay night club in the city of Orlando in American state of Florida which left over 100 people dead or injured was carried out by an Islamic State fighter.
The suspected shooter was identified by authorities as 29-year-old Omar Mateen.
Two US officials familiar with the investigation said that no evidence had yet been found showing a direct link between the massacre and IS or any other militant group.
The officials told Reuters news agency that they also had yet to see any direct contacts between any extremist group and the suspect.
Employees at a gun shop refused to sell Omar Mateen bulk ammunition because he was acting suspiciously.
The Orlando mass shooting - the worst in modern US history - has reignited the gun control debate in America.
Omar Mateen is said to have called Orlando's News 13 about 45 minutes after the shooting at the Pulse nightclub began.