Two of the world’s largest Christian aid agencies are working together to respond to the 6.3-magnitude earthquake that struck New Zealand’s second largest city Tuesday, killing at least 65 people.

The powerful earthquake struck during the lunchtime rush, falling tall buildings, splitting concrete highways, and toppling the iconic spire of Christchurch Cathedral in the central square. Tuesday’s quake is one of the country’s worst natural disasters.

“We have been in communication with our New Zealand colleagues since the earthquake struck,” said World Vision Australia CEO, Tim Costello. “World Vision New Zealand has offered practical support to the Salvation Army who is working on the ground.”

Costello said the group’s main concern at the moment is for the children of Christchurch who may be traumatized by the earthquake.

“Our New Zealand office has partnered with parenting agency Parents Inc. to distribute a practical guide for those caring for children during this time,” Costello noted.

So far, 13 out of the 14 staff of World Vision’s office in Christchurch have been accounted for.

This is the second major earthquake to have struck Christchurch in the past six months. Last September, Christchurch suffered from a 7.1-magnitude quake that caused an estimated $3 billion in damage, but no deaths.

At least 100 people, including students, are said to be trapped under rubble, according to The Associated Press.

“It was horrific. People were covered in rubble, covered in several tons of concrete,” said Nathanael Boehm, a web designer and witness of the earthquake, to AP. Boehm added that he thinks some of the people have been crushed to death by the rubble.

The airport in Christchurch is closed, and power and telephone lines have been knocked down. Also some water pipes exploded, causing flooding on the streets.

Rescuers are currently working to save people from under collapsed buildings.

“It is just a scene of utter devastation,” said Prime Minister John Key to 3 News New Zealand. “We may well be witnessing New Zealand’s darkest day.”