Medics were initially told that about 50 workers were caught under concrete in the site at a university in Qassim, northwest of the capital Riyadh.
But they found "two persons dead" and took six others with serious injuries to hospital, a spokesperson for the Saudi Red Crescent Authority told AFP.
Eight others were slightly hurt and between three to six others were believed still trapped, he said.
Bandar al-Roshodi, the university spokesperson, told Saudi television news channel Al-Ekhbariya that the workers on the site were mostly from Pakistan.
"Until now we are searching," he later told AFP.
The trapped workers were of "different nationalities," Roshodi said. Asked about the chances of more survivors, he said: "We have hope, God willing."
Pictures from the scene showed a sprawling but low-level construction site, where many steel support rods had collapsed along with other parts of the structure inside a wide circular area.
COMMENTS (4)
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ