Story highlights Mayor: The duck boat tour operator says it's pulling its vehicles from city streets for now

North Seattle College says four students in international program were killed

Two patients remain in critical condition and nine are in serious condition

Seattle (CNN) At least four international college students were killed when a tour bus and a duck boat tourist vehicle collided Thursday morning in Seattle, officials said.

The students attended North Seattle College, which said several students are in critical condition, while other students and a North employee had serious injuries.

"Because the deceased were international students, government officials are working to contact next of kin," the school said. "We extend our deepest condolences to the families of these deceased students, as well as to the students and employee who sustained injuries."

In the hours after the accident, fire officials said 44 people were hospitalized, 12 of whom were in critical condition.

Those most seriously injured were taken to Harborview Medical Center. As of Thursday evening, two people were still in critical condition and nine were in serious condition. They were in intensive care, spokeswoman Susan Gregg said.

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