Described as being from sub-Saharan Africa , a group of four men were pulled from the sewage system by police in Nador, the Moroccan town at the border.
All four were hospitalized but one man died while the other three were treated and discharged, according to the Moroccan press agency MAP.
In recent months police and border guards have discovered ever more inventive, and dangerous, attempts to cross into Spain.
Migrants have been found squeezed inside car bumpers, spare wheel wells and the dashboard of vehicles to cross into Spain's north African enclave.
While last year a boy was discovered curled up inside a suitcase.