As rescue efforts stretched past sundown, separatist authorities were accused by Ukraine's government of failing to do enough to save the lives of the miners.
The blast occurred before dawn more than 1,000 meters (3,200 feet) underground at the Zasyadko mine in the city of Donetsk in the coal-rich Donbass region. Nearly a year of bitter fighting by pro-Moscow rebels and Ukrainian troops in the east has killed more than 6,000 people.
Rebel officials said the accident was caused by the ever-present danger of methane gas, rather than artillery fire.
There were contradictory accounts of the toll of dead and missing by the rival authorities. The rebel government that controls Donetsk was slow to divulge information, while a senior official in the capital of Kiev was swift to give a death toll of 32, only to retract it several hours later.
The blast occurred as 230 workers were in the mine, and nearly 200 of them were quickly evacuated, but uncertainty lingered throughout the day about dozens of others.
Rebel officials insisted into the afternoon that only one person had died. But a slightly wounded miner who gave his name only as Sergei told The Associated Press that he saw five bodies being pulled out.
By nightfall, Yuliana Bedilko, a representative for the rebel-managed rescue services at the site of accident, said another 23 bodies had been located below ground, bringing the overall number of confirmed dead to 24.
Under cover of darkness, a truck pulled up in the heavy rain to the mine's opening in preparation to take the bodies away. A woman emerging from the mine was heard wailing in grief from a distance.
Rebel officials had said earlier that 32 workers were unaccounted for, suggesting 16 still remained trapped as of the evening. A news agency run by the separatist government reported that 14 people were injured in the accident.
Igor Murygin, a 42-year-old miner being treated for burns at a hospital in Donetsk, said he was blown off his feet by the explosion.
"When I came to, there was dust everywhere. People were groaning," said Murygin, who suffered burns over 20 percent of his body.
The mine had recently installed new equipment and nothing appeared to be out of order, he added.
Speaking in Kiev, Ukrainian Prime Minister Arseniy Yatsenyuk accused rebels of preventing a team of 60 Ukrainian rescuers from reaching the mine to provide assistance. But leading rebel representative Denis Pushilin denied that Ukrainian authorities had offered any help.
"If we truly need assistance, we will turn to Russia," Pushilin was quoted as saying by the rebel-run Donetsk News Agency.
Miners arriving for their morning shift ended up doing most of the work to clear away debris. Reaching the stricken section was complicated because the entrance that was closest to the accident had been shut by the artillery fire that has beset Donetsk.
Separatist officials arrived at the mine throughout the morning, but all refused to respond to questions, frustrating relatives of miners looking for answers.
Valentina Petrova came to the mine looking for her 47-year-old son, Vladimir.
"He was supposed to retire next year. Everyone is angry that they say on TV that 32 people died, but nobody tells us anything," she said.
The mine has a history of deadly accidents, including one in November 2007 that killed 101 workers, and two more the following month that killed a total of 57.
Workers complained about many safety violations at the site.
"We work like crazy for peanuts. We want this place to be safe. We want our children to be able to work here," said a miner who only gave his first name, Kostya.
He told the AP that two of his brothers had been injured in earlier explosions at the mine.
Safety officials say 99 people were killed in Ukraine's coal mines in 2014, with 13 of those deaths directly attributable to the fighting in the east, where mines have frequently been hit in artillery duels.
Associated Press writer Peter Leonard in Kiev contributed to this report.