At least 150 people are dead following an explosion at a gas station in Ghana’s capital where many people were taking shelter from torrential rain and flooding, President John Dramani Mahama said Thursday.

Mahama told journalists Thursday evening that the country would observe three days of mourning for the victims and that the government would allocate about $12 million for relief operations and to repair damaged infrastructure.

Billy Anaglate, a spokesman for Ghana Fire Service, said crews were recovering charred bodies at the scene Thursday morning.

The cause of the overnight explosion was not immediately known. Neighbors say many people had gone to the station amid heavy flooding in the area.

"We are still trying to salvage the site of the accident before we can come out with an accurate figure," Anaglate told reporters, referring to the death toll.

Graphic footage aired on national television early Thursday showed corpses being piled into the back of a pickup truck, while other scorched bodies were trapped amid the debris. Neighboring buildings that had caught fire burned into the night as floodwaters hampered rescue efforts.

"Many people took shelter under a shed at the station during a severe rain across the country and got trapped when the explosion happened," Michael Plange, who lives a few blocks away, told The Associated Press.  

The explosion occurred near the Kwame Nkrumah Circle, in the center of Accra.  

Police public affairs officer Cephas Arthur told the public to stay away from the scene.  

"We must allow the Fire Service and National Disaster Management Organisation to work to find trapped bodies at the scene of explosion," he said.  

State radio reported that Accra and other cities across the country have been flooded.

The Associated Press contributed to this report