In a CNN interview with Wolf Blitzer, Kelly explained that he doesn't know any information about what Trump has alleged. However, "if the president of the United States said that, he has his reasons to say it, he has some convincing evidence that that took place."
Kelly also confirmed to Blitzer that he is considering separating women and children at the US-Mexico border.
"Yes, I am considering -- in order to deter more movement along this terribly dangerous network -- I am considering exactly that," Kelly said. "They will be well cared for as we deal with their parents."
Both FBI Director James Comey and former Director of National Intelligence James Clapper refuted Trump's claims.
You can see the full interview below: