The explosion blew out the windows of nearby houses in downtown Conakry, and hundreds of residents fled the area, eyewitnesses said.
The authorities have ordered schools in the city to close and urged workers to stay at home.
The explosion was caused by a fire. It is unclear what started the blaze.
“Eight charred bodies were brought to the morgue of the Ignace Deen hospital,” a senior official at the facility told AFP news agency.
Media reports of the number of people injured vary from 84 to 100.
The blaze and billowing black smoke could be seen miles away, Reuters news agency reports.
Government spokesman Ousmane Gaoual Diallo told the BBC that he could not confirm casualty figures because “we still haven’t finished counting the number of victims”.
A crisis unit has been set up under the prime minister to deal with the fire, and its aftermath, Mr Diallo said.
Source: 3news.com|Ghana