Police in Fort Madison are investigating a threat at Fort Madison High School.
Police are questioning students and all schools are on lockdown, according to district officials.
Students alerted high school officials to a concerning text that was very general in nature and not specific to anyone or any place, Police Chief Bruce Niggemeyer said.
"The messages were not specific, but were concerning to the school officials and to the school resource officer," he said in an email statement. "As a precautionary move, all four schools were placed on lockdown."
Police located the student who sent the text message and determined that he wasn't a threat.
The schools remain on lockdown as police continue their investigation.
The district says students are secure and that offices are getting numerous phone calls from concerned parents. Parents are welcome to pick up their students from school, but are asked to contact their respective schools directly.