Photos of the scene shared on social media showed groups of rescuers working their way through a crumpled heap of steel girders and concrete.
Preah Sihanouk province and its largest town, Sihanoukville, has seen a rush of investment in recent years from China, especially into the casino, property and tourism sectors.
Home to Cambodia's largest port and a Chinese Special Economic Zone connected to Beijing's Belt and Road initiative, the town is also undergoing a construction boom to serve those growing crowds of Chinese tourists and investors.
The collapsed building is Chinese-owned, according to Saroeun.
Police have detained four people, including three construction supervisors, for questioning in relation to the accident, according to a statement from the province.
Reuters