The alleged mass-killing, if confirmed, would be one of the worst of the militant group's many atrocities against civilians.
But Reuters has since withdrawn its report, saying the source of the claim had been "misattributed". Dead or alive and in the hands of the IS group, the fates of the workers remains officially unconfirmed.
Analysts have suggested that the reported mass murder may have come in reaction to IS battlefield losses in Anbar province, with the militant group lashing out after being "cornered".
Confusion reigns over the 300 employees that have, according to some reports, been unreachable since Monday.
"The company has informed the industry ministry that it hasn't been able to make contact with the kidnapped individuals," reported the state-run SANA agency.
But the same agency also reported that 106 of the workers had been handed over to a "reconciliation committee" on Wednesday.
| | |
| Video: IS fighters have been pushed back on several fronts, with Russian troops now clearing mines from Palmyra |
Earlier local reports suggested the Islamic State group had kidnapped 250 cement workers from the east Damascus factory.
"We haven't been able to reach our family members since noon on Monday after an attack by [IS] on the factory," said a resident of the town of Dmeir, 50 kilometres (30 miles) east of Damascus.
"We have no information about where they are," the resident told AFP earlier this week.
The Syrian Observatory for Human Rights said "dozens" of staff were believed to have been seized by IS from the cement factory and taken to an unknown location.
| Read more:250 Syrians 'missing' after IS attack; feared kidnapped |
The Badiyah cement factory lies outside Dmeir, which has seen fierce fighting in recent days as government forces shelled IS positions inside the town.
IS attacked the town of Dmeir after suffering a series of territorial losses at the hands of regime troops in recent weeks, including in the ancient city of Palmyra as well as their main supply route to Turkey on Thursday.
At least 18 civilians were killed in the government shelling while 20 members of regime forces and 35 IS fighters had also been killed in the clashes.
A Syrian security source told AFP that IS fighters had also tried to seize the nearby Dmeir airbase and power plant from the government but had failed.
More than 270,000 people have been killed and millions have fled their homes since Syria's conflict erupted in March 2011.