Madrid, Spain (CNN) -- Three Spanish aid workers kidnapped in Mauritania appear to have been abducted by al Qaeda, Spain's interior minister said Monday.
"Everything points" to al Qaeda as being responsible for the kidnapping, Alfredo Perez Rubalcaba, the interior minister, told reporters in Brussels, a senior aide traveling with Rubalcaba told CNN.
Rubalcaba said he was not absolutely certain it was al Qaeda, but added that he's concerned that "we are facing a kidnapping by Islamic radicals."
The three aid workers from the Barcelona Solidarity Action humanitarian organization were traveling in a car Sunday that got separated "for unknown reasons" from the rest of a 13-vehicle aid convoy.
They were traveling from Mauritania southward toward Dakar, in neighboring Senegal, Spain's Foreign Ministry said in a statement Monday.
There was no immediate claim of responsibility nor has there been any contact with the presumed kidnappers, Spanish Foreign Minister Miguel Angel Moratinos said on Monday in Portugal, where he was attending a meeting.
Moratinos said he has talked to the presidents of Mauritania and neighboring Mali, and the three countries have agreed to cooperate in trying to find the hostages. Spain is sending aircraft to aid in the effort.
The search was broadened to Mali, the western neighbor of Mauritania, to try to prevent the hostages from being moved further afield, Moratinos said.
The vehicle was noticed missing around 7:30 p.m. local Mauritania time on Sunday, when the other vehicles stopped to make a security check of the convoy, and noticed that one vehicle was missing, Moratinos said.
They soon found it, but empty, with the doors open and with tracks from another vehicle leading away into the desert, Moratinos said.
The abduction occurred on a road between the coastal cities of Nouadhibou and Nouakchott, the capital of Mauritania, Moratinos said.
Spanish news reports said the vehicle was the last in the convoy and authorities found valuables, including money in it. The reports added that the assailants were armed.
But the Spanish Foreign Ministry could not immediately confirm those details, a spokesman in Madrid told CNN.
At Spain's request, troops from Mauritania are now escorting the rest the convoy, the ministry said.
The aid agency and the three people kidnapped are well known in Barcelona, news reports said.
Spain's Foreign Ministry said it has sent an official to help the rest of the convoy and is trying to gain the release of the three.