The TODAY Show 'fact checks' Donald Trump about 911, President Obama's birth certificate

Donald Trump isn't backing down from controversial comments he made on the TODAY Show Thursday, but how accurate were the things he said?

Trump says everything with certainty. Take this about the 9/11 terrorists. "The terrorists, almost every single one of them sent their families back a day early. You know they all went to Saudi Arabia," he said.

But, there is no evidence that families of the 9/11 hijackers were in the United States. Some Bin Laden family members were flown out after the attack, after being screened by the FBI.

In his exclusive interview with Meredith Vieira on "TODAY" Trump spent time questioning whether President Obama was born in the U.S., demanding that the president produce his actual birth certificate.

"He doesn't have a birth certificate or he hasn't shown it. He has what's called a certificate of live birth and that's different. If you look at it, it's not even signed by anybody. Doesn't have a serial number," he said.

The certificate of live birth does have a serial number and a stamped signature and Hawaiian officials say it carries the weight of law. If one of your parents is an American citizen you could get a certificate of live birth in Hawaii even if the child wasn't born there but the document states Obama was born in Honolulu and a Hawaiian official say original records verify the president was born there. And there is a birth announcement nine days after President Obama was born, information the paper says would have come from the hospital.

Trump said, "His grandmother in Kenya said he was born in Kenya."

That's based on a recording of a 2008 interview with Obama's elderly grandmother conducted through a translator. Initially the translator said she was present for her grandson's birth.

Translator: "Yes, they say that yes she was. She was present when President Obama was born."

Listen and the answer changes. When the interviewer says he wants to visit the hospital in Kenya where Obama was born he's repeatedly corrected saying Obama was born in Kenya.

Translator: "No. Obama was not born in Mombasa. He was born in America."
Interviewer: "I thought he was born in Kenya."
Translator: "No. He was born in America. Not in Mombasa."

Trump said he stands by everything he said. He also argues that none of the evidence cited definitively prove that the president was born in Hawaii.

He says he has investigators out there still digging.