Crews have successfully removed the charred Toronto Hydro transformer that caused Monday's explosions from its underground vault, but there's still no word on what caused it to burn in the first place.

Just after 11 p.m. on Tuesday, hydro crews wrapped up their cleanup of the vault beneath the Royal Bank building at 20 King Street West.

This transformer exploded in an underground hydro vault on Monday afternoon. There is no word yet on the cause. (CBC)

"Until we get all the equipment out and get a good look at it, and have a full investigation done, we don't know exactly what the cause is unfortunately," said Toronto Hydro spokesperson Tori Gass.

Nobody was hurt in Monday's explosions, which took place at about 5:15 p.m. and which filled the street with thick smoke. Since the incidents occurred during a downpour, it's not clear yet if weather was a factor.

Gass said hydro crews had to wait until Tuesday for Toronto Fire Services to deem the vault safe enough to access.

"There was three levels of soot going down to the sub-basement and there was a significant amount of damage in the transformer room," Toronto Fire Services Platoon Chief Kevin Aucoin told CBC News.

It's not the first time hydro vault fires have paralyzed parts of downtown. Last March subway service was suspended during the morning commute following a hydro vault fire.

Back in 2014, a similar issue sent staff rushing out of Toronto City Hall. Three people had to be treated for smoke inhalation.

Toronto Hydro says it has some 11,000 vaults in all, and the majority are downtown. They are inspected every three years.

The vault on King Street was last checked this fall, and was in good working order.