"Social media posts that CBP is detaining Iranian-Americans and refusing their entry into the US because of their country of origin are false," the agency tweeted on Sunday.
It also said that neither the Department of Homeland Security (DHS) nor the CBP, a subordinate of the DHS, has issued a related directive, reports Xinhua news agency.
The statement was in response to a viral tweet alleging that "more than 60 Iran & Iranian-Americans of all ages were detained at length and questioned" at a border crossing in Blaine, Washington state.
Washington Governor Jay Inslee on Sunday that the DHS has informed his office that they did not issue an order to detain or refuse entry to Iranian-Americans.
"However, we are continuing to seek answers from federal officials and talk to those caught at the border," Inslee said in a tweet.
"My office is closely tracking reports that Iranian Americans, including US citizens and lawful permanent residents, have been detained at the WA-Canada border."
Tensions between Washington and Tehran are running high after The January 3 US airstrike in Iraq killed Iranian Major General Qasem Soleimani.
The killing has sparked outrage in Iran which has vowed to retaliate.
While US cities are ramping up security in the wake of the situation, authorities have said that there was no specific, credible threat against America.
( With inputs from IANS )