MADRID—Spanish police say they have arrested a Spaniard who possessed a small amount of material that could be used to make explosives and had city maps which highlighted several embassies in Madrid.

Police said in a statement Tuesday the man was detained in a Madrid hotel where he had a 1.5-liter (0.4-gallon) bottle containing potassium nitrate, sulfur and coal dust, as well as a manual entitled "Homemade bombs and explosives."

The statement said he also had maps where the American, Chilean, Paraguayan and Brazilian embassies were marked, though authorities had no confirmation he intended to attack those buildings.

Police identified the man only as 48-year-old Alberto R.M. and said he was arrested Sunday after a hotel owner raised the alarm.

He had no known links to terror organizations or radicals.