Olympic organisers have cancelled diving training and shut the pool in an attempt to restore the water to its original blue colour, three days after its emerald hue stirred concern among competitors.

The pool turned green on Tuesday, becoming the subject of numerous jokes and creating a headache for organisers. An adjacent pool used for water polo and synchronised swimming has also started to change colour.

Perhaps the closure was just as well, as Germany's Stephan Feck reported on his Facebook page that the venue smelled like farts.

"The moment you want to do some workout and the pool is closed — the whole venue smells like somebody has fart," he wrote, with a picture of himself holding his nose at the pool.

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Despite promises to restore the colour of the pool at the Maria Lenk Aquatic centre by Wednesday evening, organisers were still trying to adjust its chemical levels, a spokesman for Rio 2016 told a news conference.

"We have learnt that chemistry is not an exact science," Mario Andrada said.

"Some things, as you can see, have gone on longer than expected."

Competitors were performing dry training in the venue on Friday, using an area where divers can practise using trampolines, platforms and harnesses.

The organisers said the pool would reopen Saturday (AEST) for training as well as for the women's individual three-metre springboard preliminaries.

World swimming governing body FINA said the colour change was the result of a failure by the organisers to sufficiently treat the water after tanks at the venue ran out of chemicals.

The organisers responded by putting more chlorine, a chemical that kills algae and helps to keep water blue, in the pool and its neighbour.

But that just resulted in water polo players complaining that chlorine was stinging their eyes.

Tony Azvedo said he could hardly open his eyes for the last quarter of America's match with France as organisers rushed to turn the water back to blue.

"What's ridiculous is not the green water. I've played in plenty of pools with green water. The problem is they put way too much chlorine in. I could barely open my eyes for the final quarter," Azvedo said.

"Who cares about the green water? The water could be any colour, it doesn't matter. What matters is that it's safe for us.

"This is the Olympic Games and they are putting so much chlorine in the water that people can't see. You can't have that."

Andrada said the discoloured water posed no health threat to competitors and was being regularly tested by health experts from the International Olympic Committee (IOC), FINA and Rio 2016.

Heavy rain in recent days had made it more difficult to fine-tune the levels of chlorine in the open-air pool accurately, he added.

Reuters/AFP