After escaping from a nature reserve last year, a herd of 15 elephants has wreaked havoc in China, trampling crops and causing more than a million dollars in damage.

According to the state Xinhua News Agency, the elephants traveled 500 kilometers (311 miles) through the southwestern province of Yunnan, from the Xishuangbanna nature reserve to Yuxi, a city of 2.6 million people, leaving a trail of destruction in their wake.

It is unclear why the elephants left their nature reserve - but on their journey, they caused 412 separate incidents of damage, costing around 6.8 million yuan ($1.1 million), according to Xinhua News Agency. They destroyed 56 hectares of farmland in Yuanjiang and Shiping alone.

Locals have been inconvenienced. After the elephants roamed the streets of Eshan for six hours Thursday, residents were told to stay indoors and pedestrians and vehicles were taken to safer areas.

Authorities blocked traffic while the elephants crossed and were setting up barriers and using food as bait to try to keep them away from Kunming and other populated areas.

Authorities set up a 24-hour command center to monitor the animals after they were spotted in Yuxi's Hongta District Monday, mobilizing more than 360 people, 76 police cars and dirt trucks, and nine drones, as well as preparing 18 metric tons of elephant food. According to Xinhua News Agency, there have been no deaths of injuries.

The herd is made up of six female adults, three male adults, three sub-adults and three calves, according to monitoring images.

Chen Mingyong, an Asian elephant expert cited by Xinhua News Agency, said this was the longest-distance migration of wild elephants ever recorded in China. Chen speculated that their leader "lacks the experience and led the entire group astray."

According to the World Wildlife Fund, Asian elephants are the largest land mammal on the Asian continent. They are a protected species in China, with around 300 of them living in Yunnan.