Their appointments were gazetted by Head of Public Service Felix Koskei on Thursday morning.
"In that regard, the National Assembly is unable to vet the nominees in the absence of an express constitutional or statutory requirement to do so," read the communique in part.
The swearing-in ceremony began minutes past 8 am.
Ruto's CASs are a significant increase from former President Uhuru Kenyatta's administration, which had 26 in number.
Among those who took the oath of office after their gazettement oath are Evans Kidero (Trade Ministry), Bishop Margaret Wanjiru, Catherine Waruguru (Foreign Affairs Ministry), Isaac Mwaura (Office of the Prime Cabinet Secretary), Eng Nicholas Gumbo (Transport Ministry), and Wilson Sossion (Tourism Ministry).
"I have deliberately appointed some of you because of your experiences and I expect that you understand service to the people and bring that experience to serve in your new responsibility," Ruto said.