Two related firecracker incidents at local high schools this week have Whitehorse RCMP investigating three people who may be responsible for the disturbances.

The vice-principal at F.H. Collins Secondary School discovered a used firecracker on the floor just after lunchtime on Tuesday, principal Christine Klaassen-St. Pierre said in an interview this morning.

The firecracker was 'small, like a birthday candle,' said Klaassen-St. Pierre, and was not in close proximity to any of the school's classrooms.

A more serious incident occurred at Vanier Catholic Secondary on Wednesday afternoon.

A teacher alerted principal Trevor Ratcliff to sounds of what were initially thought to be gunshots.

The sounds were coming from a back hallway, Ratcliff said in an interview this morning.

The teacher thought it sounded like a semi-automatic firearm due to the number of 'popping' sounds.

Ratcliff contacted the RCMP and ordered a lockdown. That meant classroom doors are locked, lights are turned off and students remain in their classrooms.

However, the same teacher noticed residue papers and blown-out firecrackers outside a classroom window and realized the sounds were coming from firecrackers, not a gun, said Ratcliffe.

The lockdown lasted for about 15 minutes, ending at 3:10 p.m., said Ratcliff.

By the time RCMP officers arrived, it had already been determined that firecrackers were the source of the popping sounds.

Cpl. Glenn Ramsay, a spokesman for the RCMP, said the incident 'is under investigation right now and there are some people identified that the investigators will be following up with.'

However, he added he wasn't sure if those identified were witnesses or suspects or both.

'We believe we know who the identity is (of those responsible),' said Ratcliff.

A passerby outside the school saw three boys 'take off and leave' during the time of the incident, said Ratcliff.

'We realized it's the same kids (behind the two incidents),' said Klaassen-St. Pierre, due to their similarities.

Students at Vanier Catholic regularly practise doing lockdowns, said Ratcliff, and in fact had practised one the same day the incident occurred.

No one was hurt in either incident.