Mr Pack said that officials found an explosive device inside the pipe, as well as another device inside the bunker.

BBC: Alabama hostage-taker died 'in firefight'

According to the criminal complaint, police were called to a Texas residence on Tuesday where they discovered bomb-making components including a galvanised metal pipe, fuse, lighter and explosive powder in bags.

BBC: Texas fertiliser plant blast: Criminal probe launched

After the rescue, authorities found the pipe packed with explosives along with another explosive inside the bunker itself, authorities said.

CNN: Inside the bunker: From storm shelter to boy's prison

In their stolen SUV they had five pipe bombs and a pressure-cooker explosive like the ones that blew up at the marathon, Kelly said.

NPR: Police: Boston Suspects Planned To Attack New York

But authorities' decision to rely on every tool at their disposal paid off: Dykes had planted an explosive device in a ventilation pipe he'd told negotiators to use to communicate with him on his property in the rural Alabama community of Midland City, and also placed another explosive device inside the bunker, the FBI said in a statement late Tuesday.

WSJ: Military tactics, arms, helped rescue Ala. hostage

As it turned out, authorities' decision to rely on every tool at their disposal was a wise one: Dykes had planted an explosive device in a ventilation pipe he'd told negotiators to use to communicate with him on his property in the rural Alabama community of Midland City, and also placed another explosive device inside the bunker, the FBI said in a statement late Tuesday.

WSJ: Military tactics, arms, helped rescue Ala. hostage

The other explosive devices allegedly in their possession -- pipe bombs and makeshift grenades -- also appear to have been basic in design.

CNN: SHARE THIS

The device was apparently a homemade pipe bomb filled with regular gunpowder as opposed to some more devastating explosive like TNT.

CNN: No Comfort for Criminals