"We have now begun the process of finalizing our report by providing a draft of our factual findings to the Department and FBI for classification determination and marking," he said in the letter.
"As I noted in my June correspondence to you, my direction to our team has been to follow the evidence wherever it leads and to complete the review as quickly as possible," continued Horowitz. "Consistent with this guidance, the team has reviewed over one million records and conducted over 100 interviews, including several of witnesses who only recently agreed to be interviewed."
Allies of the president have accused members of the former administration of illegally surveilling the Trump campaign after the 2016 election.
Defenders of the Obama administration say the actions were legal and necessary as a part of the investigation into Russian interference in the election, and now unsubstantiated suspicions of collusion.
President Donald Trump began the very public firestorm himself when he tweeted in March 2017 the allegation that the Obama administration had ordered his "wires tapped" at Trump Tower just before the 2016 election.
Terrible! Just found out that Obama had my "wires tapped" in Trump Tower just before the victory. Nothing found. This is McCarthyism!— Donald J. Trump (@Donald J. Trump) 1488627320.0
In response to the tweet, Sen. Lindsey Graham (R-S.C.) said at the time that it would be an enormous national scandal if proven true.
"The president of the United States is claiming that the former president of the United States ordered wiretapping of his campaign last year," said Graham. "I don't know if it's true or not but if it is true, illegally, it would be the biggest political scandal since Watergate."