Some 384 people, including 91 children, are now believed to have died in the explosion at Oaks Colliery, as 400 miners worked underground in December, 1866. The figure is 23 more than previously recorded.
Another 27 people died when rescuers were caught in a further explosion a day later.
Volunteers from the Dearne Valley Landscape Partnership said burial records suggest 169 bodies were never recovered and remain in old pit workings beneath the Hoyle Mill, Ardsley, Kendray, Monk Bretton and Stairfoot areas of Barnsley.
The group‘s community officer Stephen Miller said: “Sadly, we knew that poor record-keeping and the chaos in the aftermath of the disaster meant that the exact number of people killed at Oaks Colliery has never been properly revealed and it has long been known that the figure of 361 was only based on an estimate by the mine owners.
“Our aim from the outset was to try and find a more accurate figure and find out more about the individual stories of those that died.”
Mr Miller added: “Our first aim was to identify and find out about the unnamed victims. The overall number was never the most important thing for us, but it was very interesting to see our list of names go beyond the 361 figure that has been accepted for so long.”
Researchers spent more than 3,000 hours going through records.
Volunteer Noel Shaw said: “This research presented an unmissable opportunity to delve into the lives of those who perished and their families, whilst also working to produce a more accurate list of fatalities.
“I was surprised to see how many people travelled the length and breadth of the country to Barnsley for employment in the dangerous coal mines.”
Commemorations of the disaster will culminate in an exhibition at the Experience Barnsley Museum in December.
The Oaks explosion was the worst pit disaster in the UK until the 1913 Senghenydd explosion in South Wales, which killed 439 miners.