A high-speed boat chase near the Spanish port city of Cadiz left one alleged drug trafficker dead and four injured when their vessel crashed into the riverbank late at night, authorities said Sunday.

Spain's Civil Guard said officers on the water backed by a helicopter began pursuing eight boats spotted entering the Guadalquivir River at full speed Saturday night, with the aim of preventing them from unloading their suspected illicit cargo. 

One boat "loaded with drugs" managed to dock next to another that the crew then used to flee, the Civil Guard said in a statement, adding that "47 bales of hashish" were left behind on the abandoned vessel. 

Members of the Civil Guard continued their chase of the boat carrying the suspected traffickers, which then accelerated before crashing head-on "at full power" into the riverbank. 

"The boat overturned, resulting in the death of one person, while four others were injured to varying degrees," the statement said. 

Another 74 bales of hashish were recovered around the accident site in addition to the drugs found on the first vessel. 

The accident comes seven months after the death of two civil guards whose boat was struck by a drug boat during a chase in the port of Barbate, in the province of Cadiz. 

The region regularly sees drug seizures by Spanish customs agents and the Civil Guard, with Spain being among the main entry points of drugs into Europe.