Last week, Rio patched its main sewage line and lifted a month-long swimming ban at most beaches. But leaks sprang in recent days in other parts of the ageing system, spewing out a fresh wave of contamination along the shoreline.

The city had to reimpose no-swimming zones on the main tourist beaches on Monday after environmental officials found high levels of pollutants in the surf that posed a risk of causing hepatitis, typhoid fever or intestinal parasites.

Locals in the trendy beach neighbourhoods of Leblon and Ipanema have protested as a dark, smelly liquid bubbled up from storm drains, polluting streets and flowing down an open canal that empties into the sea.

Residents of Leblon, which has the highest property tax rates in the city, erected a banner on the beach demanding that the authorities clean it up.

"Now we have to ask them to clean our sidewalks because that stuff gushing out is certainly not petroleum. What new disgrace will happen with Leblon?" residents association president Joao Fontes told reporters.

City officials, worried about damage to Rio's crucial tourism industry, have demanded an explanation from the state-owned water utility Cedae for the rash of breakdowns and are negotiating to take control of the waste disposal system.

The cash-strapped state of Rio has opted to repair, rather than replace the decades-old infrastructure, with an eye to building a sewage treatment plant eventually, government officials have said.