International aid workers reaching the site of Thursday's train explosion in North Korea report finding total devastation for hundreds of meters in every direction.

North Korean officials acknowledged that at least 154 people are confirmed dead and 1300 were injured. Seventy-six of the dead were children whose school was flattened by the blast.

A North Korean statement says the explosion at a railway station in Ryongchon, a city near the border with China, was caused by carelessness as rail cars containing ammonium nitrate fertilizer came into contact with an electrical charge.

However, the Chinese news agency reports that an oil tanker collided with rail cars containing fertilizer, knocking down an electricity pole, which triggered the blast.

A United Nations team, including representatives from the Humanitarian Affairs Office, UNICEF, the World Health Organization, and the International Red Cross, was sent to the region after North Korea formally requested international assistance Friday.

South Korea has pledged to send $1 million in emergency aid to the North. China, North Korea's closest ally, also pledged to send medical supplies, tents and food worth $1.2 million.

In a statement released Saturday, Pyongyang's official Korean Central News Agency expressed appreciation for the humanitarian assistance being rendered by foreign governments and international organizations.