Two Michigan school districts have banned students from bringing backpacks to campus, with one of the districts citing several recent incidents of students bringing guns to school.

Grand Rapids Public Schools announced Wednesday it is banning backpacks after a loaded handgun was discovered in a third-grader's bag -- the fourth confiscation of a handgun from a student this academic year, according to a statement from the district.

The weapons were found in backpacks in three of the four incidents, the statement said.

"This is not a decision we've taken lightly and we know this poses a significant inconvenience for our families. I am more than frustrated that a decision like this is necessary, but we must put safety first and that's what this decision is about," Grand Rapids Public Schools Superintendent Leadriane Roby said. "This is just one step in an ongoing conversation about how we can best protect our children in our rapidly-changing world."

The ban will be in place "until further notice," the statement said.

The new policy in Grand Rapids came just days after another Michigan school district, Flint Community Schools, banned backpacks as of May 1.

"We have reached a point where we must make difficult decisions" to ensure school safety, Flint school officials said in a statement announcing the backpack ban.

The decisions made across the two Michigan districts come at a time when schools across the US are struggling with how to prevent and prepare for mass shootings on campuses, including conducting mass shooter drills and installing metal detectors.

According to a CNN count, there were at least 16 shootings at K-12 schools in the US in which at least one person was wounded from the beginning of the year through March 27. That's when six people, including three children, were killed in a shooting at the Covenant School in Nashville. In January, a teacher at an elementary school in Newport News, Virginia, was shot by a 6-year-old student who brought a gun to school in his backpack, police said.

"Across the country, we have seen an increase in threatening behavior and contraband, including weapons, being brought into schools at all levels," Flint school officials said in their announcement.

"By banning backpacks altogether and adding an increased security presence across the district, we can better control what is being brought into our buildings," the Flint release said.

The ban was approved by the Flint Board of Education and district administrators and is supported by the Flint Police Department, according to the news release.

"This is a difficult decision, but it is one that will immediately benefit our district and the safety of those we serve," the release stated.