Rescue teams are rushing to save people trapped in extremely cold weather by a magnitude-6.2 earthquake that jolted Jishishan county in Northwest China's Gansu province late Monday evening.

"Based on past rescue, the biggest difficulty of this operation is the local low temperature," Wang Duo, a team leader from the Gansu Houtian Disaster Rescue Center, was quoted as saying by China News Weekly.

The first group of rescuers arrived at the scene by 9 am Tuesday, with the second group close behind.

The temperature differential between day and night in northwestern China during winter is substantial. Currently, low temperatures are around -10 C, Wang said, adding that the trapped people are at great risk.

"The earthquake occurred in midnight, and many people did not have time to seek shelter," Wang said.

Rescue personnel are trying to speed up the rescue process. Wang said the typical golden rescue time for earthquakes is 72 hours, but it's shorter under the current weather conditions.