People enjoying rides during last day of CNE, in Toronto, September 5, 2011.
Credits: Alex Urosevic/Toronto Sun/QMI Agency
No one was injured during the 3:51 a.m. blast that caused an estimated $30,000 in damages and shook the ground for kilometres.
The explosion took place in a vacant parking lot in between two bridges.
Toronto police Staff-Sgt. Steve French said experts will be at the scene today to conduct tests. The Ontario Fire Marshal's office is investigating.
"They will be conducting a damage assessment to determine the exact cause," French said. "At this point, propane may or may not be involved."
Toronto fire officials said it appears there was a small propane tank and the valve may have been left open. The tank was empty and some residual propane may have filled the trailer and could have been sparked by the generator, officials said.
Officers said the blast occurred in an area where many people could be during daytime hours. The fair grounds was closed at the time.
Police say the trailer is owned by the Black River Food Company and was taking part in a food truck rally.
The CNE's operation won't be affected, officials said.