Minister of Interior Sar Kheng on Saturday blamed sub-standard construction for the collapse of a six-storey building that killed at least seven people and injured 18 others in Kep province on Friday.

Sar Kheng said police have detained several people, including the construction owner, for questioning.

"There's no other reason besides the poor quality of construction. All constructions are legally required to go through thorough inspection [by relevant authorities]. In this case, the company contracted to oversee this project must have failed to follow it.

"We have not determined whose fault it is yet, but we have detained several people," he said.

Sar Kheng stressed that the authorities were placing top priority in the search for the more than 30 people believed to have been trapped under the debris.

"After that, we will look into whether there was any illegal practice involved in the construction. We will strictly apply the law in bringing those most responsible to justice," he said.

As of 2pm on Saturday, rescuers found two more survivors and sent them to hospital for intensive care.

Meanwhile, Prime Minister Hun Sen has announced financial support for the families of the dead and injured.

"To help relieve the victims' grief, I would like to contribute 40 million riel [$10,000] to each of the injured and 200 million riel plus 10 million riel towards the funeral expenses of each family of the dead," he said in his Facebook page.

Hun Sen, who is currently at the site overseeing rescue efforts, said he had received nearly $1.5 million in donations.

Keo Tit, a 44-year-old residing close to the site, said the construction had been underway for several months before the collapse.

While he did not know what would become of the project, he said the workers came from different provinces.

Ung Oeun, a survivor from Prey Veng province who was being treated at the provincial hospital, on Saturday told The Post: "I was rescued at about 7pm on Friday evening.

"I got stuck under sacks of cement and shouted for help. Then I crawled out little by little. There were perhaps more than 40 people in the building, including the workers' children, some of them as young as four months old," he said.

In a statement on Saturday, the Kep provincial administration said 30 per cent of the debris had been cleared amid ongoing search for those trapped.

The Building and Wood Workers Trade Union Federation of Cambodia (BWTUC) on Saturday called on the government to extend the National Social Security Fund (NSSF) to construction workers and to take tough action against those most responsible for the tragic collapse.

It also urged the government to form a committee to carry out technical inspections and check the quality of all constructions across the Kingdom.

It said an audit of all construction companies across the country should also be carried out to prevent dangers to workers.