the victims were between age 15 and 17.

A Wisconsin high school teacher facing federal child pornography charges was charged Wednesday in Minnesota with trying to secretly record students in their Minneapolis hotel rooms on a business club trip.
Hennepin County prosecutors charged David Kruchten, 37, of Cottage Grove, Wisconsin, with three felony counts of interfering with the privacy of a minor under 18.
Kruchten is a teacher at Madison East High School and was chaperoning students on a trip to Minneapolis in December. Authorities allege Kruchten hid cameras in a smoke detector and two air fresheners planted in students' hotel bathrooms at the Hyatt Regency in downtown Minneapolis.
Kruchten was indicted  by a federal grand jury on child pornography charges last week. Minnesota authorities issued an arrest warrant for Kruchten, who is being held in Wisconsin.
According to the Minnesota complaint, the alleged victims were all girls between the ages of 15 and 17.
Minneapolis police were called to the hotel on Dec. 8 on an invasion of privacy call and learned that "suspicious surveillance devices" were found in three rooms where "multiple teenagers" were staying for a conference. Officers learned that Kruchten had delivered two air freshener canisters — later determined to contain surveillance cameras — to the front desk.
Kruchten told hotel staff that the devices were in the cabinet of student rooms instead of that the devices actually were found positioned in bathrooms "in places where the likely intent was to capture sexual imagery," the complaint said.
The automatic air fresheners and a smoke detector were "oriented to face toward the toilet and shower area. One of the victims noticed an air freshener on her bathroom counter and went to press a button that she believed would activate the spray. When she pressed it, the device opened up to reveal the inner workers of a surveillance camera and other related electronics," the complaint said.
The students in those three rooms reported their rooms were not cleaned on Saturday, Dec. 7, and that the devices were found that night. A member of the hotel cleaning staff told investigators a man who matched Kruchten's description said that the rooms did not need to be cleaned, according to the complaint.
Kruchten told investigators he had removed some thermostats from walls in the rooms of the students and had given the thermostats and a smoke detector to a security guard, but his description of the guard's uniform did not match what hotel staff wears, the complaint said.
Police found that the air fresheners had been modified to hold tiny cameras and battery packs. The other devices were never found. Officers searched Kruchten's cellphone and found he had an account with a company that sold electronic equipment and had purchased surveillance cameras built to look like smoke detectors, air fresheners and thermostats, according to the complaint.
Kruchten was placed on leave in December after the students found the hidden cameras and the investigation was launched. Kruchten has taught in the Madison district since 2008, most recently as a business education and marketing instructor, according to his LinkedIn biography. He was listed as the assistant girls tennis coach on the high school's website.
Minnesota court records do not list a defense attorney who could comment on Kruchten's behalf. Kruchten's attorney on the federal charges, Joseph Bugni, declined to comment Wednesday, but earlier said he'll build a defense around authorities' failure to recover any images from Kruchten's devices.