Malaysia's health ministry said on Wednesday three more people had been infected with the new coronavirus, taking the total to seven, all of whom are Chinese citizens.
The new cases involve a 4-year-old girl, a 52-year-old man and the mother of two children confirmed infected earlier, the ministry said in a statement.
Authorities said the mother had initially tested negative and had stayed in Malaysia to take care of her children - grandsons of a 66-year-old man who tested positive in Singapore for the coronavirus last week.
Separately, Malaysia's communications regulator said it has detained one person accused of spreading fake news on the coronavirus.
The person was arrested over a Facebook post that contained false information on the outbreak, the Malaysian Communications and Multimedia Commission said.
The newly identified coronavirus, which originated in the Chinese city of Wuhan, has created alarm because it is spreading quickly and much about it is still unknown.
China's National Health Commission said the death toll from the coronavirus outbreak in the country had risen to 132 as of end-Tuesday, with a total of 5,974 cases confirmed.
Malaysia this week imposed a temporary ban on Chinese nationals arriving from Wuhan and surrounding Hubei province.