Five workers were crushed to death and three others injured while extracting stones at a quarry in Kalairag area of Companiganj upazila on Sunday night.
They were digging in a pit when a massive chunk of earth fell over them.
In Jaintiapur upazila, another worker died after he was critically injured in a similar incident yesterday morning.
As many as 16 workers died in the illegal quarries of Sylhet in the last two months.
After Sunday night's incident, three of the workers' bodies remained buried in the pit for hours.
The victims are Motiur Rahman, 30, Ruhul Amin, 22, Ashik Ali, 38, Atabur Rahman, 30, and Moyen Uddin, 32, said Dilip Kanti Nath, inspector of Companiganj Police Station.
In a Jaintiapur quarry, Delowar Hossain, 26, was critically injured in the morning and died hours later in a hospital, Moinul Jakir, officer-in-charge of Jaintiapur Police Station, said.
Two probe committees were formed to investigate the Companiganj incident.
The district administration formed a three-member probe body headed by Additional Deputy Commissioner Mohammad Abdullah while police formed a two-member probe committee headed by Additional Superintendent of Police Abul Hasnat.
The committees were asked to submit their reports in seven days.
Police detained Abdur Rouf, who hired the workers from the quarry.
Last year's death toll in illegal quarries in Sylhet was 32.
On January 2 this year, five workers died while extracting stones in Jaflong area.
Illegal extraction of stones continues in four upazilas of Sylhet ignoring the risks of fatalities and serious injuries.
Abul Lays, Companiganj upazila nirbahi officer, told The Daily Star that the administration was trying to stop illegal stone extraction. Sometimes cases are filed against stone extractors.
A taskforce formed with administration, Police, Border guards and environment department officials has been working for three years to curb stone extractions.
“Illegal stone traders should not get bail easily,” he said.
Abdul Karim Kim, general secretary of Bangladesh Paribesh Andolon (BAPA) in Sylhet, said the matter had gone far beyond environment concerns, as over a hundred workers were killed in recent years.
“The traders are exploiting workers without providing the least safety or medical support.”