BISMARCK, N.D. (AP) — Authorities in southern North Dakota say the FBI has been contacted after a laser beam was aimed twice at an aircraft doing surveillance of an ongoing oil pipeline protest.

The Morton County Sheriff’s Office on Monday said a pilot reported a laser beam entering the cockpit and leaving him temporarily blind Wednesday. Then, on Sunday, the pilot was able to look away in time to avoid the laser.

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Morton County Sheriff’s Office spokeswoman Donnell Preskey says the North Dakota Highway Patrol was flying the state plane.

Directing a laser at an airplane is a federal offense.

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Protesters have disrupted construction of the $3.8 billion Dakota Access Pipeline that’s designed to carry North Dakota crude to Illinois.

Construction has been temporarily shut down until a federal court hearing. A federal judge on Monday pushed the hearing to Sept. 8.

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