A Defence Force ordinance disposal team was deployed to Horowhenua College today after a potentially explosive chemical was discovered in the school's science lab. police say.Emergency services were called to the school about 10.20am.In a post on social media principal Grant Congdon said the school's science technician discovered a "flask of chemical material which was identified as potentially unstable"."The work of removing the material was undertaken by the professionals. It was exploded on our back field at approximately 3 pm," Congdon said.Congdon wrote that "under supervision of the experts" all staff and students were made safe.A police spokesperson said the science block was evacuated and there were no reports of injuries stemming from the incident.Horowhenua College has been approached for further comment.