Six players from the Spain squad had money stolen from their hotel rooms in Recife while they played their Confederations Cup opener against Uruguay, Spanish media reported on Thursday.
The players affected, including Barcelona defender Gerard Pique, made the discovery after the world and European champions' 2-1 victory over Uruguay on Sunday.
"We know there was a report, a police report and this was being dealt with by the relevant authorities, we have been in touch also with the team," FIFA spokesman Pekka Odriozola told a briefing.
"We are waiting to hear from the authorities. [We] don't have all details. We know there was an incident and the police are investigating."
Spain take on Tahiti in Rio in their second Group B match later on Thursday.