The improvised explosive device (IED) that failed to fully explode in London early Friday was manufactured with the Islamic State’s signature chemical, United Kingdom Security Minister Ben Wallace confirmed Saturday.

The chemical is known as TATP and has been used in a multitude of ISIS attacks across the continent, including the November 2015 Paris attacks, the March 2016 Brussels attack, and the 2017 Manchester attack on an Ariana Grande concert. The London IED still managed to put nearly 30 passengers on the metro system in the hospital, causing some severe burns.

ISIS correspondent for The New York Times characterized TATP as the terrorist groups “signature” explosive in Europe, in a tweet Friday.

An 18-year-old man was taken into custody as of Saturday in connection with the attack, but police are still on the hunt for other suspects. The device’s chemical composition comes as no surprise after ISIS claimed responsibility for the attack Friday, promising more explosions to come.

TATP is particularly attractive to ISIS bomb-makers in Europe because it can be manufactured relatively quickly from household materials. The bomb likely failed to fully explode because a crude timing device malfunctioned.

“This absolutely didn’t function properly because…one ounce of TATP is enough to blow car doors off,” former head of counter-terrorism at the Ministry of Defense Major General, Chip Chapman, told The Independent after the attack. Source.