- Explosion occurred as residents gathered to buy cooking gas
- At least four people are dead, the Red Cross says
Local media reported death tolls as high as 100 in the Christmas Eve incident in Nnewi city.
But the local Red Cross team said it counted four bodies and another four injured. Anambra state police declined to comment on the conflicting number of casualties.
Although he did not provide a specific number of casualties, President Muhammadu Buhari said he was "greatly shaken and shocked by such large-scale loss of human lives."
"My heart and prayers go out to these grieving families at this difficult and painful moment," Buhari said in a statement.
The blast and ensuing inferno occurred as residents gathered to buy cooking gas, said Chume Ibeabuchi, who oversees records at the local Red Cross.
It's common for residents to take their cooking gas cylinders for refilling -- especially in preparation for holiday festivities.
"The truck caught fire and exploded while offloading gas which engulfed the whole factory and surrounding buildings," said Godwin Ibe, a resident of Nnewi.
Cause of blast unclear
Ibeabuchi said he organized a Red Cross response team that arrived hours later and found police, military and fire officials at the scene.
While the exact cause of the blast is unclear, it appears someone filling up on gas did not follow the proper procedure, he said.
Nnewi is a predominantly Christian city about 280 miles east of Lagos.