Miami, Jul 1 (IANS): The death toll from the collapse of a residential building in the US state of Florida has increased to 18 after the bodies of two children were found in the debris, local authorities have confirmed.

"I'm pained to tell you we found two additional bodies in the rubble, which brings our total count to 18 -- 18 fatalities," Xinhua news agency quoted Miami-Dade County Mayor Daniella Levine Cava as saying at a news conference late Wednesday.

"It is also with great sorrow, real pain, that I have to share with you that two of these were children. Aged four and 10," Cava said.

"Any loss of life, especially given the unexpected, unprecedented nature of this event, is a tragedy," said the Mayor.

"But the loss of our children is too great to bear."

The National Institute for Standards and Technology (NIST), a non-regulatory federal safety agency within the Department of Commerce, is expected to announce that they will launch an investigation to determine the technical cause of the collapse of the building located in Surfside.

The NIST probe is also likely to offer recommendations for changes to building codes, standards and practices or other appropriate actions to improve the structural safety of buildings, so that similar tragedies hopefully could be prevented in the future, CNN reported, citing a senior administration official.

A thorough investigation by the NIST could possibly take years to complete, said the report.

Meanwhile, a 2018 report has emerged, in which engineers raised concerns about the structural damage of the condo built in 1981.