Chinese Foreign Ministry spokesperson Hua Chunying also said the recent tests showed that the water quality met the standards of Class III water.
Class III is generally regarded as good for fish regeneration and wildlife.
Earlier, media reports spoke of heavy pollution in the Brahmaputra river known as Siang river in Arunachal Pradesh.
Some media outlets quoted reports of formation of barrier lakes in Tibet close to Arunachal Pradesh which has sparked concerns of a possible deluge in the downstream.
"We have noted that Indian media recently made a series of reports on this issue. They said China was conducting water conservancy project or exploiting a mine previously whereas now claim there is a barrier lake upstream," Hua said.
"I could tell you responsibly that none of these speculations is true according to the results of the investigation by the relevant Chinese authorities," she told news agencyPTI in response to a question.
She said the 6.9-magnitude earthquake in mid-November hit the area near Mainling County in Tibet, "which might have lead to the turbidity in the middle and lower reaches of the river for a certain period of time".
"After the earthquake, we monitored the water quality of the Yarlung Zangbo (Chinese name for Brahmaputra) River and the results showed that it met the standards of Class III water," she said.
At the same time, she stressed that the investigation done by China is "utterly for humanitarian considerations and does not affect its stance on the border issue."
Hua yesterday said that China will maintain communication with India to deal with massive lakes formed by landslides on the Brahmaputra river in Tibet following the earthquake, which caused concerns of a sudden flooding on the Indian side.
She said verification by the relevant Chinese authorities revealed that the lake is to the "eastern section of the India-China boundary".
"It is caused by natural factors. It is not a manmade accident. I noticed that Indian professional authorise have made an analysis and clarified," she said, referring to reports that the lakes were formed by the landslides.
China hopes that the Indian media will not make groundless speculation on this, she added.