The train was traveling between Evian and Thonon-les-Bains when it struck the bus carrying 50 children and six adults near the Swiss border, The BBC said Monday.
Initial reports indicated at least 30 people were injured in the crash and a sixth person may have died as a result of the accident, but there was no word on whether the victim was an adult or a child.
"All of us are thinking of the children, the adults, the victims," said French President Nicholas Sarkozy. "We can only hope there will be as few victims as possible."
Train passengers suffered only minor injuries.