The accident, which took place just before sunrise on a road around 50 kilometers from the southwestern Andalusian city of Huelva, involved a bus carrying 34 Moroccan agricultural workers, the 112 emergency services said.
"One woman died and 25 others have been injured, including seven in very serious condition, when a bus carrying seasonal workers overturned," the 112 said on the regional government's website.
It was not immediately clear what caused the accident in an area known for its vast agriculture industry, with the Andalusia region Europe's top exporter of fruits and vegetables.
In a separate statement, medics with the CES emergency services said "34 workers were travelling on the bus; one of them died in the accident, seven others were seriously hurt and 18 others were slightly injured".
In remarks ahead of May Day marches, Labor Minister Yolanda Diaz offered her "condolences and deepest sympathy to the workers caught up in this very serious accident".
Spain traditionally relies on thousands of seasonal workers from abroad to pick fruits, with the Huelva province producing around 90 percent of the European strawberry harvest at this time of year.
Moroccan Workers In Fatal Spain Crash
update
UPDATED TO SHOW HIGHER INJURY COUNT: MADRID - A bus carrying Moroccan seasonal workers overturned early on Monday in southern Spain, killing one person and injuring 39 others, three of them seriously, the emergency services said.
