Eight of the accused, all senior managers, are charged with murder over the Soma coalmine tragedy in western Turkey last year.
The trial was adjourned until Wednesday because the court said the accused must testify in person, not via video link.
An underground fire sent deadly carbon monoxide through the mine. An inquiry criticised the mine's safety measures.
It was modern Turkey's worst industrial accident.
The trial at Akhisar, about 50km (30 miles) from Soma, drew several hundred angry relatives to the special tribunal, but police prevented them from getting in.
The BBC's Turkey correspondent Mark Lowen says the government is shielding state officials from any investigation, despite claims that they were aware of safety deficiencies at the mine but failed to act.
The managers facing murder charges could be given up to 25 years in prison.
Protests broke out after last year's disaster, fuelled by an apparently insensitive comment by President Recep Tayyip Erdogan, who was prime minister at the time. He said accidents were "in the nature of the business".
The International Labour Organisation says Turkey has the third-highest rate of workplace accidents in the world.

They ran in seven tries to finish second in Pool Three and book their British & Irish Cup quarter-final spot.
"There was some sloppiness in there that we'll have to rectify in the week," Cattle told BBC Radio Cornwall.
"I thought the score flattered us a little bit - it was only in that second 20 minutes in the first half where they missed a few one-on-ones."
Alex O'Meara scored a hat-trick at the Mennaye, with captain Chris Morgan, Bar Bartlett, Jake Parker, and Alex Day also going over.
Pirates had Marlen Walker sin-binned while fly-half Bartlett suffered a rib injury, with the club awaiting results from an x-ray.
"Us coaches are always going to be picky with the performance," added Cattle.
"When we had the sin-binning it looked a little bit disjointed from the scrum but they're things we can iron out."

President Evo Morales has announced a contingency plan, which includes $700,000 in extra funds for fumigation.
The swarm first appeared over a week ago near the low-lying eastern city of Santa Cruz, where most of Bolivia's food and meat is produced.
It has spread quickly, destroying pasture and fields of corn and sorghum.
The authorities estimate more than 1,000 hectares of agricultural land have been devastated by the locusts.
The government says fumigation must begin straight away.
"We will create a 500-metre-wide ring around the area affected and fumigate inside, working alongside the local authorities," said Bolivia's Agriculture Secretary, Mauricio Ordonez.
Mr Morales is due to visit Santa Cruz province on Friday.
Turkey has begun the trial of 45 managers and employees charged over a mine disaster which killed 301 people.
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Cornish Pirates coach Gavin Cattle says his side has room for improvement despite their 50-24 win over Connacht.
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The Bolivian government has declared a state of emergency in a vast agricultural area affected by a plague of locusts.