CAPE TOWN, May 7 (Xinhua) -- The death toll from the collapse of a building under construction in South Africa on Monday has increased to six, with 48 still trapped beneath the rubble, authorities said on Tuesday.

The multi-story building collapsed on Monday afternoon in the coastal city of George, located about 400 kilometers east of Cape Town in the Western Cape province. The reasons for the collapse of the building, which included an underground parking garage, are still under investigation.

In an update on Tuesday noon, the municipal government of George said "27 patients have been removed from the rubble of the collapsed multi-story construction site at 75 Victoria Street, leaving 48 persons unaccounted for." It confirmed that six patients have been declared deceased.

"Seventy-five construction workers were present on the site at the time of the collapse which occurred at 2:09 p.m. on Monday, May 6, and the rescue operation is now approaching 22 hours as of 12 p.m. today, May 7," it added.

More than 100 emergency personnel are currently involved in a rescue operation to retrieve the trapped construction workers, aided by several volunteers and civil society groups, according to the Western Cape government.

"I want to express my most sincere condolences to the families and colleagues of the victims of the building collapse tragedy in George. My thoughts are with them during this exceptionally difficult time. Our priority right now is saving lives," said Western Cape Premier Alan Winde in a statement issued by the provincial government.

"Everything possible is being done to expedite this very delicate operation," he said. "We will continue to do everything we can to support the ongoing search and rescue and recovery operation underway ... Further resources will be made available if and when they are required."

Meanwhile, South African President Cyril Ramaphosa called for an investigation into the cause of the building collapse and offered his condolences to the relatives and friends of those who have died in the incident. "The president's thoughts are with the families who have lost loved ones as well as the families of close to 50 people who are trapped in the rubble," said the presidency in a statement.

"President Ramaphosa wishes rescue teams the best as they go about their operations and says investigations into the cause of the incident must aim to bring closure to the community and prevent a repeat of this disaster," it added.