Updated

At least 10 girls and women have been raped on the Fort Apache Reservation by a man who poses as a police officer, federal authorities said.

Since March, nine girls and one young woman — all American Indian — have been attacked on a trail between two housing projects between 10 p.m. and 2 a.m., said officials with the Bureau of Indian Affairs.

The attacks began in March, but the bureau became aware of them only in August. The agency formed a task force of 10 agents to investigate.

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"Once they saw it was involving someone posing as law enforcement, the BIA made this a high priority," said BIA agent Warren Youngman.

Bureau officials said Wednesday they had identified the four newest victims after the task force canvassed the neighborhood where the attacks occurred.

The panel found victims who did not come forward because they thought their attacker was a police officer, Youngman said.

"It has created an atmosphere of fear," Youngman said. "When we did our neighborhood canvassing, we had people afraid of our officers."

The attacker is believed to be American Indian, 20 to 40-years-old and of medium height and build.

According to victims, the attacker wears a dark shirt and a dark baseball cap, both bearing "police." White Mountain tribal police officers' uniforms do include black shirts, but the shirts should show a badge above the left breast pocket and a U.S. flag above the right breast pocket, Youngman said.

There is a $10,000 reward in the case, Youngman said.

The reservation is about 80 miles northeast of Phoenix.