Investigators have so far found "no connection" between international terrorist groups and a mass shooting in Las Vegas that killed at least 58 people and injured more than 500, an FBI special agent said Monday.

The Islamic State group, through its propaganda arm, had earlier claimed responsibility for the attack, claiming the shooter was a recently converted "soldier." Police said the attack was carried out by Stephen Paddock, a 64-year-old retired accountant.

"As this event unfolds we have determined to this point no connection with an international terrorist group," said Aaron Rouse, the special agent in charge of the Las Vegas office of the FBI.