Spanish website Ciclo21 reported that police in the country were scrutinising his connections to Dr Marcos Maynar, a professor at the University of Extremadura, who is under investigation for alleged drug trafficking and money laundering.
Lopez, initially a witness in the case, was intercepted at the Madrid-Barajas Airport by police in connection to the investigation into Maynar, the media report said, adding that the allegations concern the distribution of medicines that are not authorised in Spain.
Lopez's agent and Spain's Guardia Civil police force did not immediately respond to requests for comment.
"The news that was spread in the media yesterday evening caught us by surprise, and at the moment we do not have any details," the team said in a statement on Twitter
"In this regard, the team decided to suspend Miguel Angel Lopez from any activity within the team until all the circumstances of the case are clarified."
One of Astana's top riders, Lopez has not competed since withdrawing from stage four of the Giro d'Italia in May with a hip injury.
He has previously won stages on the Tour de France and Vuelta a Espana, and is a past winner of the Tour de Suisse and the Volta a Catalunya.