The Air Force’s Office of Special Investigations is reviewing what happened Monday when a C-17 plane was swarmed by hundreds of people at Kabul’s airport and, later, human remains were found in the plane’s wheel well after it landed in Qatar.

A dramatic video taken earlier Monday showed some people clinging to the plane as it taxied down the runway in Kabul.

A defense official said the individuals swarming the plane had breached the runway from the civilian side of the airport. Air operations were suspended for hours at the airport Monday because of the crush of Afghan civilians desperate to leave Kabul.

"OSI is leading the review in coordination with the U.S. Air Force’s Air Mobility Command and international partners since it involves the loss of life on U.S. military aircraft," Air Force spokesperson Ann Stefanek said in a statement. "OSI’s review will be thorough to ensure we obtain the facts regarding this tragic incident. Our hearts go out to the families of the deceased."

-ABC News' Luis Martinez

State Department spokesperson Ned Price said in a briefing from the agency on Tuesday that the U.S. remains cautious, yet prepared after the Taliban said it will allow for the safe passage of Americans and Afghans who aided in the U.S. mission to leave the country.

"We have also said there has been engagement with the Taliban on the ground in Kabul. This is a military-led channel. It's a channel that is tactical, that, again, is focused rather squarely on issues like safe passage for civilians," Price said. "It is manifestly in our interests to have these open channels of dialogue with the Taliban."

He said the government has received "assurances" but acknowledged the U.S. response in the coming days will depend on the group's actions.

"We're going to be looking for the follow-through. We'll be looking for the deeds," Price said.

He also said the State Department is dispatching career diplomat John Bass, who formerly served as U.S. ambassador to Afghanistan, to Kabul "to lead logistics coordination and consular efforts," as the race to evacuation thousands continues.

U.S. Citizenship and Immigration Services is asking for volunteers to help process Special Immigrant Visas for Afghan nationals and their families, according to an agency-wide email obtained by ABC News.

The agency says it has set up a temporary field office at Fort Lee in Virginia but could also deploy volunteers from across the agency to other locations throughout the country "to support rapid response temporary on-site immigration processing and adjudications."

The email notes that as the situation in Afghanistan evolves "USCIS is working with departmental agencies to determine the total number of processing sites needed at various U.S. military bases."

In addition to USCIS personnel, a Department of Homeland Security spokesperson said agents from Customs and Border Protection are also helping process SIV applications.

-ABC News' Luke Barr

Gen. Frank McKenzie, head of U.S. Central Command who is the top U.S. military commander in the Middle East, visited the airport in Kabul Tuesday.

McKenzie confirmed the visit, which was kept secret for security reasons, in a statement.

“I saw firsthand our defensive lay down and the work our forces are doing to efficiently operate the airfield while ensuring the safe movement of civilians and diplomats who are leaving Kabul,” he said in the statement.

“Currently, the airfield is secure and now open to civilian air traffic operating under visual flight rules,” he added.

He restated that he met with Taliban leaders over the weekend in Doha, where he said he "cautioned them against interference in our evacuation and made it clear to them that any attack would be met with overwhelming force in the defense of our forces."