Spanish police have arrested two men accused by the US of being leading members of Mexico's Juarez drug cartel.
Israel R G (left) and Joel F C, in a picture released by Spanish police
The suspects, identified only as Joel F C and Israel R G, were detained on a plaza in central Madrid, after police traced them to a high-class hotel.
Washington issued international arrest warrants for the Mexicans as part of an inquiry which has led to the seizure of 250kg (550lb) of cocaine in the US.
Joel F C, 42, is accused of organising marijuana deliveries to Texas.
Israel R G, 28, is alleged to have helped collect money from the sale of drugs in the US and then smuggled it back into Mexico.
They were arrested on the Plaza de la Lealtad, home of the Madrid stock exchange and the Ritz hotel.
If found guilty, the two men could face several life sentences in the US, Spanish police said in a statement.
The Juarez cartel, based in the city of Ciudad Juarez, specialises in trafficking Mexican marijuana and Colombian cocaine across the US border.
Recent US police raids in states bordering Mexico have netted $7m in cash, as well as the 250 kilos of cocaine.
The drug cartels in the area have also been engaged in a turf war this year, leaving more than 500 people dead.
In 2001, Mexican police arrested a man accused of heading the Juarez cartel, Ramon Alcides Magana.