State investigators are looking into whether a rural Minnesota police chief engaged in criminal activity by sending sexual messages to a young woman this month.

A restraining order against Montevideo Police Chief Adam Christopher was approved by the Chippewa County District Court on Nov. 15. In it, an 18-year-old woman said she and Christopher had sent hundreds of text messages to one another starting when she was 17, but his messages became sexual this month.

The city has launched its own investigation into the complaint and has asked the state’s Bureau of Criminal Apprehension to investigate if any criminal activity took place, City Manager Steve Jones said Tuesday. If no criminal charges are warranted, the city could still take disciplinary action against Christopher.

“We’ll certainly do our best to investigate them,” Jones said of the complaint.

Christopher went on personal sick leave Nov. 19 and it’s unclear when he will return to work, Jones said.

In the restraining order, the 18-year-old said Christopher is the father of a taekwondo classmate and a Facebook friend, and they began messaging each other when she was 17.

“I usually conversed with him because I didn’t know how else to respond,” she wrote, adding that his messages became sexual this month. “He stated that I am ‘tempting. … Behave, or I will come up there and cuff you.’ ”

In another message, he said he would stalk her if he was near her home, she said. The restraining order prohibits Christopher from contacting her or being near where she lives or works for two years. “He is in a position of authority and could harm me,” she wrote.

Christopher has been with the department since 2001. He’s been the city’s police chief since 2006, according to the department’s website. Jones said no other formal complaints have been filed against Christopher.