"Keyes" mission

I promised myself to pass through every Halo campaigns before getting into Halo 5: Guardians, to really assimilate the story line. So, I just finished Halo: Combat Evolved, and unfortunately, one of my many questionings is still unanswered.

In the mission “Keyes”, after getting to a hangar of the Truth and Reconciliation, there’s a large hole in the floor just past the door. What kind of explosive caused it exactly? Is it explained in the books or somewhere?

> Cortana: “Analyzing damage… This hole was caused by some kind of explosive. Very powerful if it tore through a ship’s hull. All I detect down there are pools of coolant. We should continue our search somewhere else.”

Might have had to do something with the coolant? My best bet is that the Flood accidentally set something off when they began to take over the cruiser.

Probably some reactive explosion with the coolant