TRENTON, N.J. - Gov. Chris Christie says he's sorry for making too much noise on an Amtrak quiet car.

Christie spokeswoman Samantha Smith says he accidentally took a seat in the quiet car while traveling from Washington on Sunday morning.

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Smith says after breaking "the cardinal rule of the quiet car," Christie promptly left for the cafe car.

She says he was talking on a cell phone when a conductor pointed out it was the quiet car. Unaware of it, Christie told the caller he would call back after changing cars.

Smith offered sincere apologies.

Conductors generally urge passengers to maintain a "library-like atmosphere" in the quiet car. It's not uncommon for conductors to ask noisier passengers to change cars.

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The Republican presidential hopeful appeared on CBS's "Face the Nation" earlier Sunday.