Officials said rescue efforts were moving slowly, impeded by the presence of dangerous gases and a lack of oxygen tanks, and had to be suspended several times while workers ventilated the mine shafts to disperse dangerous gases.
Luis Alfredo Ramos, the governor of Antioquia province, said 70 to 72 people were believed to be inside the mine when the explosion, which the authorities believe was caused by a methane gas buildup, occurred on Wednesday night.
On Friday, more than 3,000 residents of Amaga, about half the rural town ringed by coffee plantations and coal mines, attended a funeral service at a local church for nine of the miners whose bodies were recovered on Thursday.
Coroners from the state prosecutor's office said most of the victims died from burns in the explosion, which happened in a 2-km long access tunnel that drops to a depth of 150 metres.
Missing safety features
Colombia is the world's fifth largest coal exporter and is enjoying a boom in mining and energy investment.
|Thousands attended a funeral for nine of the miners on Friday [Reuters]
But the disaster will put the spotlight on mining safety regulations in the industry which ranges from large deposits operated by multinationals to hundreds of small, often illegal, makeshift pits that produce coal for local markets.
Compounding the shock and grief of Amaga residents – witnesses to the deaths of dozens of miners over the years – was the fact that the San Fernando mine was a legal operation which should have had proper safety features, our correspondent said.
Hernan Martinez, the mining minister, said the mine, located just south of the Antioquia state capital of Medellin, lacked a methane ventilation pipe and gas-detection devices - basic safety features in coal mines – and would not reopen until an investigation into the cause of the blast was completed.
But Jorge Buitrago, the general manager for the mine, owned by Carbones San Fernando, told the Associated Press news agency that it complied with safety requirements for monitoring and controlling gases.