Spanish police have arrested three suspected terrorists, Spanish media reported Wednesday. The three have been linked to the international Al-Qaeda terror organization.

Al-Qaeda issued a warning in July saying that Spain may be attacked by “lone wolf” terrorists.

The three were in possession of explosives and poison, and are believed to have been planning an attack.

One of the three is a Turkish citizen. The two others may be of Chechen origin. At least one had been trained in Pakistan.

In 2004 terrorists bombed a train in Spain, murdering 191 people. The 2004 attack is thought to have been linked to Al-Qaeda.