Members of Spanish civil guards and rescue workers carry bodies in El Palmar, Spain's Canary Islands Feb. 11, 2007. The bodies of six tourists have been retrieved from a flooded cave in Spain's Canary Islands, emergency service officials said on Sunday. (Xinhua/AFP Photo) Photo Gallery>>>

MADRID, Feb. 11 (Xinhua) -- The bodies of six tourists have been retrieved from a flooded cave in Spain's Canary Islands, emergency service officials said on Sunday.

    The bodies of the five men and one woman were found by rescuers in the Piedra de los Cochinos cave on the island of Tenerife. Initial examinations indicated the deaths were probably caused by a lack of oxygen or inhaling of toxic gases.

    The six victims were among a group of 30 adventure tourists, all between 20 and 30 years old, who launched an expedition last weekend into the underground tunnel complex in the Tenerife island, a famous tourist attraction frequented by adventurers and nature lovers.

    The expedition had been led by a guide who couldn't make it to the scene but gave instructions by a mobile phone.

    "They entered the water tunnel by accident. It was not part of the excursion. That error may well have been the reason for this serious accident," Espana Angel Yusel, of the Civil Guard, told local radio.

    After the tourists were trapped some 2 km underground on Saturday, one person managed to get out to make emergency calls.

    Due to toxic gases and complexity of the tunnels, it took rescuers about 17 hours to pull out the bodies, which were then flown in a Civil Guard helicopter to Los Portelas for forensic examinations at the Legal Medicine Institute in La Laguna.

    Six others who were injured were also taken to hospital.

    The tunnels were carved out to extract water on the islands off the west coast of Africa. Explorations of the tunnels is discouraged by officials, but tourists are attracted by their beauty.