An administrator at the plant in the town of Dumeir, 50 km (30 miles) east of Damascus, said on Thursday 250 employees had been unreachable since Monday.
"We haven't been able to reach our family members since noon on Monday after an attack by Daesh on the factory," the AFP news agency quoted a resident as saying.
The UK-based Syrian Observatory for Human Rights said "dozens" of staff were believed to have been kidnapped by Daesh from the Badiyah cement factory and taken to an unknown location.
The factory, which lies on the outskirts of Dumeir, has been the scene of fierce clashes between Daesh militants and Syrian government forces in recent days.
The militants have sought to wrest control over Dumeir airbase and power plant, but have been unsuccessful so far.
Meanwhile, three people were injured when two rockets fired by Daesh militants struck two different areas in the southeastern Turkish city of Kilis close to the border with Syria.
The first projectile hit a house, where Syrian refugees were living, at around 8:45 a.m. local time (0545 GMT) on Thursday. Two Syrians inside the house were wounded in the attack.
Pictures broadcast by Turkish television networks showed the rocket had badly damaged masonry and windows of the building.
Security forces immediately cordoned off the area, and ambulances ferried the wounded to a nearly hospital for treatment.
Another rocket shell struck a road and exploded, leaving one person wounded. Police forces evacuated a school nearby.
The Turkish military fired on what it called Daesh positions in northern Syria in retaliation. There were no immediate reports of casualties and damage.
Syria has been gripped by militancy since March 2011. The so-called Syrian Observatory for Human Rights says at least 270,000 people have been killed in the conflict; however, some reports put the death toll as high as 470,000.
Damascus accuses Saudi Arabia, Turkey and Qatar of funding and arming groups operating in Syria, including Daesh.
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