Barrie police say three men and a woman were taken to hospital after the explosion Friday night.
A man and woman remain in critical condition, while two men are in stable but serious condition.
Sgt. John Brooks said it's suspected the explosion was caused by marijuana resin being extracted in the garage.
Police issued a news release late Saturday saying they obtained search warrants and would be continuing their investigation, but did not elaborate.
Police say two of the injured were 37 years of age, one was 20 and the other was 24.
Investigators say there were a total of eight children and two other adults in the house. The children ranged from three weeks of 15 years.
They were all removed safely. Five children were treated for minor injuries and either released at the scene or later released from hospital. The children are now in the care of other parents or adult relatives.
The Ontario Fire Marshalls Office is involved in the investigation.