By Saturday morning, 18 people had been rescued, injured but alive, and crowds watched in the afternoon as two more survivors were pulled out and rushed to ambulances more than 20 hours after the accident.
Kep provincial authorities said in a statement that in addition to the seven people who died, 20 were injured in the disaster.
The website of the National Police reported that the Cambodian couple who owned the property and hired the construction workers were detained by provincial police for questioning on Saturday.
Prime Minister Hun Sen went to the coastal province of Kep on Friday "to lead the rescue team," he announced on his Facebook page. He also visited the provincial hospital where the injured were being treated. Several of the hospitalized survivors were reported to be in critical condition.
Nguon Samet, deputy police chief of Kep province, said Saturday morning that it was believed some people were still trapped under rubble, but he could not say how many. Relatives of some of those still missing gathered outside the site to pray, he said.
Nguon Samet had said that the seven-story building apparently collapsed Friday when concrete was being poured on its top level. Kep provincial authorities announced that a committee had been formed to officially investigate the cause of the accident.
The collapse of a building under construction last June in Sihanoukville, another coastal province, killed 28 construction workers and injured 26 others, underlining concerns about the area's rapid development and inattention to safety. The coastal area has been rapidly built up to cater to a booming tourism industry.
In December, a Buddhist temple collapsed while under construction in Siem Reap, home of Cambodia's famed Angkor temples, killing at least three people and injuring 13, including two monks.