Previously unpublished footage from the storming of the Capitol on January 6 last year was played when the hearing began in the US Congress.
A police officer who was at the scene during the riots testified about the violent scenes that took place and about colleagues who were injured in what was described as "a bloodbath".
At the same time, the then Minister of Justice and also the Presidential Adviser, William Barr, explained how he rejected Donald Trump's claim that the election was rigged.
The former president's daughter Ivanka Trump also said in a pre-recorded video that she never questioned the election result.
Trump critical of investigation
Donald Trump, who is at the center of the investigation, is now attacking.
In a statement, which has been published on Trump's own social media platform Truth Social, he calls it all a political conspiracy.
He writes that the committee "refuses to play up some of the many positive testimonies and statements that exist, refuses to talk about electoral fraud and belittles that it happened on a large scale", according to the Independent.
He further writes that the committee, which he states is acting on its own merits, "decided to use a documentary filmmaker from Fake News ABC to reinforce only the negative image".
However, Trump has not mentioned which positive witnesses he wants to appear.
"The biggest and best movement"
The ex-president is accused of inciting and setting fire to the riots that led to the congress being stormed.
Among other things, he is said to have said that the mob "may have been right" when they chanted outside Congress that Vice President Mike Pence should be hanged.
Just hours before the hearing began last night, Donald Trump wrote on his platform that he insisted that the election was rigged in favor of Joe Biden.
He also praised the storming of the Capitol.
"January 6 was not just a protest, it was part of the largest and best movement in our nation's history to make the United States amazing again," reports AFP.