Spain’s Interior Ministry has released an undated video clip that it claims shows suspected Al Qaeda terrorists training for a bombing attack using a model plane and explosives.

The grainy and low quality video footage shows the model plane taking off. Once it is airborne, a small object is released from the plane and drops to the ground. The video then shows a man running to the area where the object landed, news agencies reported. 

Spanish authorities have taken three men into custody on suspicions that they were planning a terrorist attack in Spain or elsewhere in Europe.

According to reports, two of the suspects are Russians of Chechen descent, identified as Eldar Magomedov and Mohamed Ankari Adamov. The third is a Turkish man named Cengiz Yalcin.

All three men were arrested Sunday on provisional charges of belonging to a terrorist organization. It was not clear whether they had yet been able to appoint defense attorneys. 

Spain’s Interior Ministry also released photographs of an underground area at Yalcin’s residence where around 150 grams of an allegedly explosive substance was discovered, according to news agencies. 

Judge Pablos Ruz of the National Court described Yalcin as an engineer who had worked in Gibraltar and had been involved in providing paragliding lessons for the Russians.

The ministry has declined comment on whether investigators believe the suspects were planning an aerial attack.