The three blasts that rocked Brussels on 22 March have sent shock waves across Europe, reminding people of the 2015 Paris attacks. Brothers Khalid and Brahim el-Bakraoui – both Belgian nationals – have been identified as two of the suspected bombers, who wrecked havoc at the main terminal of Zaventem International Airport in Brussels and the Maelbeek metro station, killing more than 30 people and injuring hundreds of others.

While investigations are underway, police recovered a peroxide-based explosive, called triacetone triperoxide or TATP, from an apartment belonging to one of the suspected bombers. Peroxide-based chemicals are highly unstable and are extensively used by terrorists to make bombs. TATP, hexamethylene triperoxide diamine (HMTD) and similar peroxide-based chemicals have been used by terrorists for decades.

Now, police suspect that bombs made from the same material could have been used in the Brussels attacks. However, there is no confirmation as yet from authorities over the kind of explosive devices used by Islamic State (Isis) militants, who have claimed responsibility for the attacks.

Other terror attacks where TATP was used

TATP was the primary explosive material used in many bombs and suicide vests in the November 2015 Paris attacks. The unstable chemical was used in the 2005 London bombings as well.

In 2009, the chemical was confiscated from Najibullah Zazi, who attempted to blast the New York City subway system. In December 2001, Richard Reid – also known as the shoe bomber – attempted to detonate a TATP-triggered explosive on a Miami-bound flight from Paris.

What is TATP?

TATP, which is also known as "Mother of Satan", is a white powdery substance obtained by reacting hydrogen peroxide with acetone under certain chemical conditions. TATP and other acetone peroxide based explosive chemicals do not contain nitrogen, hence, can evade nitrogen bomb detectors.

According to Washington Post, an army explosive ordnance disposal technician said that TATP-based explosives, because of their unstable character, are rarely used in war zones such as Iraq or Afghanistan. However, it has become a staple for terrorists in Europe because of the easy accessibility of chemicals required to make it.

Hydrogen peroxide is often used for medicinal purposes on wounds, while acetone is used in certain cosmetic products like hair bleach and nail polish thinner and both these chemicals can be easily purchased from retail outlets or chemists. In Brussels, police recovered around 40 gallons of acetone from the apartment of one of the suspected bombers, which could have been possibly used in making the bombs.

The Paris connect

Reports suggest that a 24-year-old man identified as Najim Laachraoui, whose DNA was found on some of the bombs used in the Paris blasts, was also involved in the Brussels attacks. He is suspected to be one of the suicide bombers in the Brussels attack, according to the Washington Post.

Reports also suggest that the bombs that detonated at the airport, could have been placed in suitcases as it would be easier to transport and chances of an accidental explosion could be reduced. In the case of the suicide bomber, it is suspected that the bomb may not have been built in a vest, as there are more chances of an accidental explosion.