BREAKING: More ISIS-K attacks in Kabul likely: source

Heinrich further reported that her source said that the "Military continues to retrograde and depart airport. Almost a certainty that Americans will be left behind. They will have to be extracted after-the-fact through either Taliban negotiation or unconventional means."

White House Press Secretary Jen Psaki had said on Wednesday that there was definitely a reason to believe that American would be left behind after the final US planes had departed from Afghanistan.

"We've sent out, as Secretary Blinken noted, 19 messages to American citizens over the course of the last few months," said Psaki. "We’ve also done a great deal of outreach and advertising, providing information for anyone who wants to leave, including the offering of financial assistance in recent weeks for people who want to leave Afghanistan."

"But what I also would note, and this is an important caveat. It is possible there could be Americans who have not yet contacted us who we don't know about. And that's why we want to leave optionality because of our responsibility to help these Americans depart," Psaki continued.

US military advisors told President Biden that a decision on whether the US would evacuate Afghanistan by August 31, or would need more time, would have to be made by Tuesday. Biden said that the deadline would not be extended.

Heinrich reported that US officials are now "pushing back on reports" that the "evacuation effort may wrap up soon."

After two explosions occurred at the airport in Kabul, the Pentagon confirmed US casualties, and Pentagon Press Secretary John Kirby said that this was a "coordinated attack."

Kirby said that: "We can confirm that the explosion at the Abbey Gate was the result of a complex attack that resulted in a number of US & civilian casualties. We can also confirm at least one other explosion at or near the Baron Hotel, a short distance from Abbey Gate. We will continue to update."

Kirby said that: "We can confirm that the explosion at the Abbey Gate was the result of a complex attack that resulted in a number of US & civilian casualties. We can also confirm at least one other explosion at or near the Baron Hotel, a short distance from Abbey Gate. We will continue to update."

Two explosions went off at the Kabul airport in Afghanistan Thursday morning. This after US state department warnings to Americans not to travel to the Kabul airport, and to leave if they were stranded outside the gates. The second explosion was reported shortly after the first.It was reported that there were at least 13 casualties and many more wounded. At least three US servicemen were among those injured in the attack.

The US embassy in Afghanistan on Thursday abruptly warned Americans stranded in the country not to travel to the Kabul airport due to terrorist threats, and asked those already at specific airport gates to leave immediately, in a statement early Thursday. The state department does not want Americans stuck outside the gates of the airport amid security threats.

"We're operating in a hostile environment, in a city and country now controlled by the Taliban, with the very real threat of an ISIS-K attack. We're taking every precaution, but this is very high risk," Secretary of State Tony Blinken said. The New York Times reports that 1,500 Americans are left in Afghanistan.