Two people have died after an accident at one of the stadiums to be used at the 2014 World Cup in Brazil.
BBC reports that the deaths occurred when a crane fell and destroyed parts of Sao Paulo's Arena Corinthians stadium.
Hosts Brazil are due to play the opening match of the tournament at the venue on 12 June.
A Fifa spokesman said local authorities would fully investigate the accident and its president Sepp Blatter said he was "deeply saddened".
A statement from the world governing body read: "We wish to send our heartfelt condolences to the family of the workers who tragically died today.
"The safety of workers is the top priority for Fifa, the LOC [Local Organising Committee] and the federal government.
"We know the safety of all workers has always been paramount for all the construction companies contracted to build the 12 Fifa World Cup stadiums.
"Please understand that we are in no position to comment further at this stage, as we are awaiting further details from the authorities."
Brazilian police say at least two construction workers were killed and a number injured in Wednesday's accident, which happened when the final part of the stadium roof, covering the north stand, was being installed.
A third man is in hospital, where his condition is not known.
Reports in local Brazilian media say there was a big crash as the crane fell on top of a metal structure, destroying parts of a stand and making construction workers dash, although most of the workers were said to be away on their lunch breaks.