Rescuers worked on Saturday to free more than a dozen miners still thought to be trapped underground at a coal pit in northern Turkey, where a methane blast a day earlier killed at least 28 people.

"58 of our miners were able to come out unharmed. We estimate that 15 of our miners are (trapped) below and we are trying to rescue them," Interior Minister Suleyman Soylu said in the small coal mining town of Amasra on Turkey's Black Sea coast.

Soylu said earlier some 110 people had been working underground when one of Turkey's deadliest industrial accidents in years struck Friday at sunset.

Relatives and friends of mine workers wait outside a coal mine after an explosion in Amasra, in Bartin Province, Turkey

According to Energy Minister Fatih Donmez, "a fire erupted in one of the tunnels after the explosion." The tunnels affected by the blast were estimated to lie 300 and 350 metres (yards) below ground.

Health Minister Fahrettin Koca earlier tweeted that 11 of those pulled out alive were being treated in hospital.

Some of the miners were able to leave the mine on their own after the blast, while others were rescued.

Television images showed anxious crowds -- some with tears in their eyes -- congregating around a damaged white building near the entrance to the pit in search of news of their friends and loved ones.

Turkish President Recep Tayyip Erdogan was due to fly to the scene of the accident on Saturday.

"Our hope is that the loss of life will not increase further, that our miners will be found alive," Erdogan said in a tweet.

"All of our efforts are aimed in this direction."

Most initial information about those trapped inside was coming from workers who had managed to climb out relatively unharmed.

But Amasra mayor Recai Cakir said many of those who survived had suffered "serious injuries".

Turkey's Maden Is mining workers' union attributed the blast to a build-up of methane gas.

But other officials said it was premature to draw definitive conclusions over the cause of the accident.

2014 disaster

Rescuers sent in reinforcements from surrounding villages to help in the search and rescue.

A woman reacts as she waits outside the coal mine

Television footage showed paramedics giving oxygen to the miners who had climbed out, then rushing them to the nearest hospitals.

The local governor said a team of more than 70 rescuers had managed to reach a point in the pit some 250 metres below.

Turkey's AFAD disaster management service said the initial spark that caused the blast appeared to have come from a malfunctioning transformer.

It later withdrew that report and said methane gas had ignited for "unknown reasons".

The local public prosecutor's office said it was treating the incident as an accident and launching a formal investigation.

Turkey suffered its deadliest coal mining disaster in 2014 when 301 workers died in a blast in the western town of Soma.