In a letter sent to US Centres for Disease Control and Prevention (CDC) director Robert Redfield on Monday, Mr Mark Pocan, a Wis-consin Democrat, noted that up until Sunday, the agency had been publicly disclosing statistics related to the coronavirus and its spread in the US, news website The Hill reported.
The data included numbers on the total confirmed and presumptive cases of the coronavirus, as well as statistics on how many tests had been administered and how many deaths had been attributed to Covid-19, the disease caused by the virus.
By Monday, the CDC stopped disseminating figures on the number of people tested and the death toll.
"Americans are dying," Mr Pocan wrote in the letter. "We deserve to know how many Americans have perished from Covid-19, and we deserve to know how many people have been tested for it."
In a tweet on Tuesday, Mr Pocan said that he had yet to receive any information from the CDC over its decision, adding that the agency's "silence is deafening".
Ms Nancy Messonnier, the CDC's director of the National Centre for Immunisation and Respiratory Diseases, told reporters that the agency stopped sharing data on the number of people tested because of more testing happening at the state level.
"We are no longer reporting the number of persons under investigation or those who tested negative," she said, according to The Hill.
"With more and more testing done at states, these numbers would not be representative of the testing being done nationally."
But Mr Pocan responded that the CDC keeps track of national health data for a wide range of diseases and should be able to keep track of testing data for the coronavirus on a daily basis.
On Tuesday, a CDC spokesman said the agency was trying to gather state testing data and might share it on the CDC website, CNN reported.