Colombia’s ELN rebel group was responsible for the car bomb attack against a police academy that killed at least 21 and injured dozens, the government said on Friday, making it unlikely that peace talks with the insurgent group can restart soon.

In Thursday’s attack, a car driven by ELN explosives expert Jose Aldemar Rojas broke through checkpoints onto the grounds of the General Santander School before it detonated, shattering windows of apartments nearby, Defence Minister Guillermo Botero said.

The attack was planned over about ten months and Rojas was killed in the blast, he said.

The National Liberation Army (ELN), made up of some 2 000 fighters and considered a terrorist organisation by the United States and European Union, began peace talks with the government of former President Juan Manuel Santos in early 2017, but they have been put on hold by President Ivan Duque until the ELN frees its 17 hostages and stops attacks.

The bombing heightens fear that a new wave of attacks could be launched in the Andean nation as a reaction to the right-wing president’s stance.

The vehicle, a grey Nissan Patrol SUV, was carrying an estimated 80 kilograms (176 lb) of the high explosive pentolite, which has been used in the past by Colombian guerrillas, Attorney General Nestor Humberto Martinez has said.

Martinez also said intercepted telephone calls helped lead to the capture of ELN rebel Ricardo Andres Carvajal Salgar overnight.

The ELN, founded by radical Catholic priests, has fought more than a dozen government’s since it formed in 1964.