OCEAN CITY, Md. (AP) -- Police in Maryland's biggest beach town say they are investigating the circumstances surrounding a series of arrests outside an underage nightclub.

The investigation by Ocean City police follows release of a Twitter video by eyewitness Andre Elder that appears to show an officer striking an individual during an arrest.

On Twitter, the person being struck is identified as a 13-year-old, according to Elder.

The Daily Times of Salisbury reports police arrested six people ranging in age from 13 to 20 Thursday outside the H2O under-21 nightclub.

Charges included disorderly conduct and assault. A police spokeswoman says no injuries were reported.

Police Chief Ross Buzzuro said Friday in a statement that the department's Office of Professional Standards is investigating. In the statement, he says the six-second Twitter video shows a small snippet of a much larger incident.

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