Spanish authorities said Wednesday they have seized over eight tonnes of hashish on the party island of Ibiza in what they said was biggest ever bust of the drug in the Balearic Islands.

Customs agents on a routine patrol came across three vans that were driving with their lights off overnight Sunday on a road linking the village of Sant Joan de Labritja in the north of the Mediterranean island to the beach, Spain's tax office which is responsible for customs said in a statement.

The drivers of the three vans "braked abruptly" causing their vehicles to collide, and their occupants fled on foot, the statement said, adding the suspects remained unaccounted for.

Customs agents found 216 bags containing 8.3 tonnes of hashish inside the vans, the "biggest seizure of hashish ever carried out in the Balearic Islands," the statement said.

The archipelago off Spain’s eastern coast, include holiday islands like Ibiza, and are among the most popular destinations for north European sunseekers.

The authorities suspect the traffickers were using Ibiza as a temporary reception for hashish which they then distributed across Europe.

Customs agents have observed a rise in hashish snuggling in the Mediterranean, especially in the Balearics, the statement said. The drugs are usually transported to the archipelago aboard "ultrafast" inflatable boats.

Spain's proximity to North Africa, a key source of hashish, and its close ties with former colonies in Latin America, the world's main cocaine-producing region, have made it a portal for drug-smuggling into Europe.