Bomb-sniffing dogs shortly before noon hit on a locker on the third floor of Memorial Middle School.

A Springfield bomb squad is at the school and at 521 S. Gray St. in Joplin where officers are searching the home.

Authorities believe there is a link between the Gray address and an incident early today at the school where a 13-year-old student walked into the school with an assault gun. No one was injured. By late morning most students had been picked up by their parents.

The student pointed the gun at two administrators and two students and then fired it into the ceiling of the school. Officials later found notes in the student’s backpack indicating that explosive devices may have been placed in the school.

There were 21 weapons incidents reported in Joplin schools in 2005, three times the state average.

Unlike today’s incident, most of those involved knives and martial arts weapons and not firearms, said Joplin Superintendent Jim Simpson.

In three previous years, the number of weapons incidents reported in Joplin was at or below the state average, according to statistics reported by public schools and compiled by the Missouri Department of Elementary and Secondary Education.

Statewide, there were 815 incidents involving weapons in 2005, according to state statistics. That is a ratio of .10 per every 100 students; in Joplin, the ratio was .30 per every 100 students, according to data reported in October 2005.

A weapon is defined as any device or instrument capable of causing serious bodily injury. It does not include a knife with a blade of less than 2.5 inches.