Dr Anthony Fauci, an infectious diseases expert and member of the White House's coronavirus task force, also criticised Donald Trump's use of the word "cure" when discussing his recovery from the illness.
Dr Fauci appears to have confirmed speculation the ceremony was a "superspreader event" that led to multiple people becoming infected.
When asked by CBS News whether masks were effective in limiting the spread of coronavirus, Dr Fauci replied: "I think the - the data speaks for themselves.
"We had a superspreader event in the White House and it was in a situation where people were crowded together and were not wearing masks. So the data speak for themselves."
When asked about Mr Trump's use of the word "cure", Dr Fauci continued: "We don't have any indication - I think you really have to depend on what you mean by a 'cure,' because that's a word that leads to a lot of confusion."
Dr Fauci also said he did not think the fact the president was heard coughing during an interview with Fox News on Thursday night was cause for alarm.
He continued: "Most people, when they recover, they recover fine. In a linear fashion, they get better and better and better, which it appears that the president is doing.
"But having a bit of a lingering cough is not at all unusual as someone recovers."
Mr Trump spent three days in hospital after he was diagnosed with coronavirus on 1 October.
Attendees were seen hugging, fist-bumping and not wearing masks at the ceremony that took place the Saturday before Mr Trump revealed he and the First Lady had tested positive.
Guests sat in tightly-packed chairs which did not appear to be two metres apart, with some of those who have since tested positive sitting close together.
In the picture above, those marked in red tested positive for coronavirus, as well as Mr Trump.
A - Melania Trump
B - Kellyanne Conway
C - Chris Christie
D - Rev John Jenkins
E - Senator Mike Lee
F - Senator Thom Tills
Donald Trump is due to speak at an event in Florida on Monday as he returns to the campaign trail following his coronavirus diagnosis.
The president is also expected to address supporters from a balcony at the White House on Saturday in an event on "law and order", an official from his campaign team said.
Mystery surrounds whether Mr Trump is still contagious and White House spokeswoman Kayleigh McEnany said medical tests will ensure that when the president is back out he will not be able to transmit the virus.
She said: "He won't be out there if he can transmit the virus."
Dr Fauci has also said he is certain Mr Trump's doctors will not allow him to leave the White House without further testing.
Mr Trump's expected return to the campaign trail comes despite the fact his second debate with presidential rival Joe Biden will not go ahead.