Greenpeace may have good cause for coming up with publicity stunts: it wants to raise awareness about environmental issues. The group, however, became a little too aggressive in its latest move.

In an attempt to send a powerful message to the participants of the Lima Climate Change Conference, a group of Greenpeace activists placed a big banner next to an ancient tracing of a hummingbird in Southern Peru's Nazca Desert.

The figure is one of a series of giant images of plants and animals that were excavated in the soil and made by the Nazca culture about 1,500 years ago. These geoglyphs, known as Nazca Lines, were designated as a UNESCO World Heritage Site in 1994 and are a very important archeological monument for the people of Peru.

Because of the fragile nature of these ancient ground figures, the Peruvian government controls visits to this historical site. Important government officials, including the country's president, cannot just go there on a whim. They need to seek permission, and those who are allowed to visit must wear special shoes to avoid damaging the site.

Greenpeace activists, however, managed to get into this restricted area to place big yellow cloth letters next to the ancient drawing. The letters read "Time for Change! The Future is Renewable."

Peru's deputy minister for culture Luis Jaime Castillo said that the activists did this in the middle of the night and in the process damaged the archeological site. The Peruvian culture ministry described this as an illegal and premeditated action.

"They went ahead and stepped on our hummingbird, and looking at the pictures we can see there's very severe damage," Castillo said. "Nobody can go on these lines without permission -- not even the president of Peru!"

Greenpeace appears to acknowledge its wrongdoing and has issued an apology for its actions. The organization also said that it will speak to the authorities to explain what happened.

"Without reservation, Greenpeace apologizes to the people of Peru for the offense caused by our recent activity laying a message of hope at the site of the historic Nazca Lines," the organization said.

The Peruvian government, however, is opening a criminal investigation and is preventing the erring activists from leaving country. Officials said that the offenders would be sought and will face charges for ruining the archeological monument, an offense that could get them up to six years in prison.