A local newspaper is reporting that Rio de Janeiro state's iconic Guanabara Bay is heavily polluted as Brazil prepares to host the "Rio plus 20" Earth Summit in June.

Rio plus 20 is scheduled for June, two decades after the first U.N. Earth Summit was held in Rio de Janeiro.

A report published Sunday in the newspaper O Globo says the first conference resulted in a vow to clean up the bay. More than $1 billion was spent building treatment plants but delays and faulty infrastructure meant they were never fully used.

Today, only one-third of the sewage from nearby cities is treated. Guanabara takes in about 10,000 liters of untreated sewage per second.

But the cleanup is more urgent than ever: Rio promised a clean bay in its bid to host the 2016 Olympics.