Police are investigating after a drone taking aerial video of a Thanksgiving Day road race in Massachusetts crashed into a pack of runners, slightly injuring two.

Andover police say the drone clipped a tree branch shortly after the Feaster Five Thanksgiving Day Race began with nearly 10,000 runners. An Andover High School teacher says he was operating it to capture "aerial perspectives of the starting line."

Police tell The Eagle-Tribune newspaper (http://bit.ly/1OC7stH ) that two male runners suffered "very small lacerations."

Daniel Brennan, who was operating the drone on a volunteer basis in his free time, had the permission of race organizers and police.

There is some confusion over whether the drone is owned by the local public access TV channel or the high school's TV program. The size of the drone also is unclear.

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Information from: The Eagle-Tribune, http://www.eagletribune.com