An Argentine judge who had investigated thousands of drug trafficking cases has been arrested on accusations he helped drug dealers in exchange for money.

The official judicial news agency says federal judge Raul Reynoso was detained Monday in the northeastern city of Salta. Reynoso denies any wrongdoing.

He had been under investigation by a local judge since late 2015, but had not been detained because he enjoyed immunity as a judge. He recently stepped down from his post.

Reynoso was a judge for more than a decade in Salta province in an area bordering Bolivia that is known as a hotbed of drug trafficking.

Traffickers are increasingly using Argentina's roads and ports as trade route for cocaine and other drugs bound for the U.S., Europe and beyond.