OTTAWA — A bus carrying about 37 tourists from China crashed on eastern Ontario’s busiest highway on Monday, and local news media and officials said about 24 were hospitalized, including at least six with critical injuries.

Aiden Liang, the manager of Union Tour Express, the company that owned the bus, said it was on a 10-day tour that began in Washington, D.C., on May 29. The crash occurred at 2:45 p.m. while the bus was traveling from Ottawa to Toronto.

Mr. Liang said all of the passengers were from China, although he did not know where they came from within the country. He said he was not certain about the number of people on board.

The bus was traveling west on Highway 401, Ontario’s main expressway, when it veered off the pavement and smashed into a rock embankment near Prescott, about 60 miles southwest of Ottawa, Canadian media reported. Photographs and video from the scene indicate that the right side of the bus was extensively damaged as it scraped along the rock face before stopping. Windows were missing, baggage doors were torn off and there was a long trail of shorn-off debris behind the bus.