(Reuters) - Workers building Rio's 2016 Olympic Park fought with security guards on Monday but although shots were fired no one was injured in the melee, eyewitnesses said.
Scuffles broke out between guards and construction workers on strike for more pay and better union representation. The workers closed several busy avenues around the site on Monday and trouble ensued.
Officials said they were examining CCTV footage to identify who fired the shots.
"The confusion took place at the work site and there were protests both there and nearby," said a witness, who requested anonymity. "Fortunately, no one was hurt."
The Olympic Park is one of the focal points of Rio's Olympic Games and will host judo, basketball, tennis, handball and cycling events at a host of purpose-built facilities.
The international broadcast center and the main media base will also be located in the park, which is being built on the site of Rio's former Formula One track.
The consortium responsible for the park, which is slated for delivery in the first half of next year, vowed the strike would not affect delivery dates.
But there is already concern at Rio's slow pace of work. Construction workers fixing the Joao Havelange stadium that is due to host the track and field events have also downed tools in protest over working conditions and low wages.
That stadium was built for the 2007 Pan American Games but was closed in March last year when engineers said the roof could fall down in high winds. Officials ordered the stadium closed and said work to shore up the structure and repair other problems would not be finished until December 2014.
The budget is also a hot topic of concern. Rio has still to decide who will pay for what and International Olympic Committee officials who visited the city on March 21 said it was crucial that federal, state and municipal authorities put their heads together and make decisions.
However, although officials said that meeting would take place in March, it is yet to happen.
Brazilian organizers have so far budgeted for 24 of the 52 projects that will be built for the Games.
Rio won the right to host the summer Olympics in 2009 and will become the first South American city to host the world's biggest multi-sport event.
Brazil will also host soccer's World Cup this June and July.
But even though the World Cup kicks off in 66 days, three stadiums are still not ready and promised public transportation and airports are also way behind schedule or have been abandoned.