A journalist at the Olympic Equestrian venue claims it tore through the canvas roof, narrowly missing a New Zealand team official.

It comes as a controlled explosion has been carried out on an unattended bag at the finish line of the men's cycling road race.

At the daily press briefing on the Olympic Park, Rio 2016 spokesman Mario Andrada had hoped to be talking about Friday night's party at the Maracana Stadium but he was immediately forced to apologise for fresh problems.

With action starting in almost 20 different sports, there are lots of empty seats at venues as spectators faced long delays to get through security.

"The main problem is in the process and system," said Andrada.

"We have people from three universes here - the national police force, military and Rio 2016 staff - and each has different processes, so it's a problem of integration.

"We've moved staff to the gates and everything will be in a much better shape within the next couple of hours.

"We apologise to anybody stuck in a line and hope they didn't miss the competition - we know we need to fix this."

Andrada took heart from the fact that some queues at the opening ceremony were only 15 minutes long, while admitting that others took 90 minutes, and said the transport plan for getting athletes back to the Olympic Village worked perfectly.

Buses laid on for the media, however, were a little more problematic, with some drivers admitting that they did not know the route between the stadium and main transport hub, while there were reports of a bus taking shooters to their venue getting lost on Saturday.

The issue of crime also resurfaced with the most serious story being a man shot dead outside the Maracana Stadium after a botched robbery.

The aftermath was witnessed by TV crews from New Zealand, the UK and US, with a BBC reporter telling Press Association Sport that the "awful" incident took place five minutes from the stadium.

Andrada said he was unaware of the reports but would investigate.

While Andrada dealt with crime and queues, IOC spokesman Mark Adams handled the now customary questions about doping, with the main topics being more Russians cleared to compete and criticism of the Brazilian authorities' pre-Games testing programme.

Adams restated the IOC's belief that the decision not to ban the entire Russian team for its state-run doping programme was the correct one, as it offered individual athletes the chance to prove their drug-free credentials, but admitted it was disappointing to see the Court of Arbitration for Sport rule against the IOC's attempt to keep out Russians with prior doping convictions.

"It's a disappointment that CAS doesn't allow us to be as tough on doping as we'd like to be, but we respect every athlete's right to go to CAS and accept its judgement," said Adams.

"We would be rightly pilloried if we went against CAS, the highest court in sport."

However, the IOC had the chance to be much tougher on doping by sanctioning the Russian Olympic Committee for failing to uphold Olympic values at home, and it was on shaky legal ground in trying to punish only Russian athletes for the same offence twice.

The court's rejection of this clear case of "double jeopardy" means the likes of four-time world swimming champion Yulia Efimova will join Russia's team but the reprieve came too late for cycling medal prospect Ilnur Zakarin.

On the issue of Brazil halting its pre-Games drug-testing regime at the end of June, in both Adams and Andrada denied there was any problem, despite the World Anti-Doping Agency already saying this was "unacceptable".