Police are investigating the strong-arm robbery of Girl Scouts who were selling cookies at a Pennsylvania supermarket.

The theft happened at a Pathmark store in Tredyffrin (TRUH'-dif-ren) Township, outside Philadelphia, around 5 p.m. Sunday.

WPVI-TV reports ( http://bit.ly/UhZ1Jz) the thief reached into a cash box containing the scouts' cookie money. He got $20 before the girls closed the box. Police say the suspect then fled to the back of the building and drove off.

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Information from: WPVI-TV, http://abclocal.go.com/wpvi