The Brussels attackers used ammonium nitrate bombs, two sources tell NBC News. The explosives were estimated at 44 pounds each.
During a raid on a residence linked to the suspects, officials found other bomb components, the Belgian prosecutor’s office said on Wednesday.More than 30 pounds of another high explosive known as TATP was found along with 150 liters of acetone and 30 liters of hydrogen peroxide, both chemicals that can be used to make bombs.
At that location, investigators also seized detonators, a suitcase full of nails and screws, plastic tubs, ventilators and glass utensils — all signs the home was being used as a bomb-making factory.
It’s not clear whether the suspects or any associates had specific plans for the rest of the materials found in raid in Schaerbeek, a neighborhood in Brussels.
TATP can be used as a booster charge to ensure a powerful detonation of a fairly stable explosive like an ammonium nitrate bomb. It can be used in a mixture with ammonium nitrate or in compact explosive devices like suicide vests.
The suspects brought three suitcase-style bombs to the Brussels Airport on Tuesday morning. They were captured on security video pushing luggage carts with large black bags through the busy terminal.
They blew up the first two bombs 10 seconds apart, officials said.
One of the terrorists dropped the third bag — which contained the largest explosive charge, and fled, the prosecutor’s office said. It exploded as the bomb squad arrived, but no one was hurt, the prosecutor said.
The ammonium nitrate was detected with swipe tests, sources said. It is a relatively stable high explosive, detonating at a speed of more than 5,000 feet per second. It is used as a key component of ANFO (ammonium nitrate/fuel oil), a popular industrial explosive.
The chemical was used in the 1995 Oklahoma City bombing and in the 1993 bombing of the World Trade Center.
Ammonium nitrate is also a widely used fertilizer. It was manufactured by the plant that exploded in West, Texas, in 2013, killing 15 people and hurting more than 200 others.
This article originally appeared on NBCNews.com.