A small plane crashed on Thursday during an aerial tour of the famed Nazca Lines archeological site in southern Peru, killing the Peruvian pilot and all six tourists on board, police said.

The Cessna, carrying three Chileans, a Peruvian couple and their four-year-old daughter, crashed as the pilot attempted an emergency landing on a road near the World Heritage Site after encountering a mechanical problem.

The plane, owned by the Nazca Airlines tour company, was completely destroyed in the crash, which occurred some 420 kilometers south of the capital Lima.

The pre-Inca site on Peru's Nazca plateau, where some 100 animal drawings dating back 2500 years are etched in the desert floor, is only clearly visible from the air.

The reason why ancient people traced the lines remains one of archeology's great mysteries.

The most common theory is that the drawings were used for rituals, while believers in extraterrestrials have cited them as evidence of alien spacecraft landings.

Five French tourists were killed in April 2008 when their plane crashed near the Nazca Lines, prompting the French government to warn tourists against flying in the country ? a recommendation criticized at the time by Lima.