ACT Policing is investigating the cause of two small fires at Garran Primary School which led to all students and staff being evacuated.

One of the fires was inside a toilet block and the other in the main school building, with minor damage at both sites.

Intensive care paramedics assessed five staff for mild smoke inhalation.

ACT Fire & Rescue put out the fires on Monday afternoon. Police ask any witnesses to call Crime Stoppers.

Police also attended the St Clare of Assisi Primary School in Conder after the remains of an exploded tin were found on the lawn near the front office.

An ACT Policing spokeswoman said the items involved in the device were a soda bottle and a mint container.

The spokeswoman said Australian Federal Police forensic investigators attended the scene but there was no damage to the building and there had been no impact on the school's classes.

Investigations continue into a suspected pipe bomb explosion in a nearby area on August 30.

St Clare's acting principal Rachel Smith said the objects were found by a staff member and may have been placed on the premises on the weekend.

"We were being vigilant because of the one that was found previously," Ms Smith said. "It didn't appear to be deactivated at any

previously," Ms Smith said. "It didn't appear to be deactivated at any recent time or on site - there's certainly no burn marks on the ground."

Last month's pipe bomb explosion occurred in parkland near a waterway and bike path between Lanyon High School and St Clare's, and was attended by Tuggeranong Patrol officers, forensic investigators and the Australian Federal Police bomb response team.

No one was injured and neither school was evacuated following the minor explosion, which caused damage to plants and grass and dispersed some material around the area.

Police also attended Ngunnawal Primary School on Monday after a domestic issue.

An Education and Training Directorate spokesman said an "unwelcome visitor" was on the school grounds, and the school followed normal processes and moved some students to another part of the school as a precaution.

"Once the individual left the school grounds classes resumed as normal," the spokesman said.