The accident occurred when a tourist bus carrying 35 Chinese people from the United States crashed on the 401 highway.
A spokesman of the Chinese Embassy said that the embassy is in contact with the relevant Canadian authorities to verify the situation. Four of those injured received life-threatening injuries, she said.
"It definitely looked very surreal and chaotic", said the man, who would only give his name as Robert. Many windows on the passenger side and both front windows were shattered.
The bus is painted with the logo of the USA -based company Union Tour Express.
The bus, which began its tour in Washington, DC, was on its way west to Toronto from Ottawa, Canada's capital, when it crashed, Aiden Liang, manager of operator Union Tour Express, told Reuters by phone.
"All of the people that we have received are all Mandarin speaking", spokeswoman Abby McIntyre said.
One Ottawa-based Ornge air ambulance has made its way back to Ottawa with a patient.
Brockville General Hospital said it received five patients who all required critical care and said one other patient was sent to a hospital in Kingston by air ambulance. "As we wait to hear more about the situation, our thoughts are with everyone hurt in the crash, and the first responders who rushed to the scene to help". Officials from the Chinese embassy visited the injured in hospital and are notifying families.