RIO DE JANEIRO — The problem of the suddenly green water in the Olympic diving pool worsened Wednesday as whatever was ailing the pool migrated (albeit in a lighter shade of green) to the nearby pool used for water polo and synchronized swimming. But Olympic officials said that after extensive tests, they had finally pinpointed the reason: a chemical imbalance caused by too many people using the water.

There had been speculation Tuesday that algae was the cause, but that theory was dismissed by officials.

“Midafternoon, there was a sudden decrease in the alkalinity in the diving pool, and that’s the main reason the color changed,” Mario Andrada, a Rio 2016 spokesman, said Wednesday morning.

He noted that a lot of people had been in the pools in the past week at the Maria Lenk Aquatic Center, and that their presence had touched off changes in the water’s chemical balance.