Police have still not said what led to an explosion Wednesday that injured a 13-year-old boy in North Charleston.

North Charleston Police spokesman Spencer Pryor said the incident remains under investigation.

The boy was injured by an explosion at 8:02 a.m. at a home on Mahi Mahi Way, according to police.

When officers arrived at the home the boy was sitting on the staircase of the home with his right arm bleeding and his hand was missing, according to a police report.

He was taken in serious condition to Medical University Hospital, according to EMS officials. By Thursday his condition had been upgraded to fair, according to hospital officials.

The Charleston County Bomb Squad was called to the home and checked the house for any other explosive device or materials, the report stated.