A stowaway was nearly poisoned after squeezing into a car's hidden compartment in a bid to get out of Morocco.
The man managed to hide in a false compartment created between the back seats of a car and the boot, which police described as one of the smallest spaces they have ever seen.
Border control officers checking vehicles at the Spanish port of Algeciras in Cadiz said the man could easily have died because of the exhaust fumes given off during the journey.
He had probably been in his hiding place for several hours after setting out from Tangier in Morocco.
"The size of the interior had been extensively modified, endangering the physical integrity of the young man because of the accumulated gases in such an enclosed space," said a police spokesman.
The car was being driven by a Spaniard living in Madrid who was arrested on suspicion of a crime against the rights of foreign nationals.
Police said the stowaway would have been unable to free himself from the space and would have relied totally on the driver to let him in or out.