Ramsey County deputies uncovered a cache of firearms, ammunition, at least one ballistic vest and explosive devices after searching a Vadnais Heights home as they investigated a school student's threat.

One juvenile and two adults are in custody, Ramsey County Sheriff Jack Serier told reporters late Friday afternoon. Serier said they are a 13-year-old boy and his parents.

Serier said the investigation began after a threat was made against a child at the Academy for Sciences & Agriculture, a public charter school that serves grades five through 12.

The child's parents reported the threat. It led to a warrant to search the Vadnais Heights home where the weapons cache was discovered.

Photos of some of the cache of guns and other items found in a home in Vadnais Heights after a threat from a boy to another student at Academy for Sciences & Agriculture (AFSA) High School & Middle School on March 2, 2018. Peter Cox | MPR News

"Many, many guns," both long guns and handguns were found unsecured in home, the sheriff said.

The St. Paul bomb squad and agents from the federal Bureau of Alcohol, Tobacco and Firearms responded to the scene. The bomb squad is "rendering safe" items found at the scene, Serier added.

The parents of the 13-year-old boy are being held on gross misdemeanor charges of negligent storage of firearms.