WASHINGTON -- U.S. immigration authorities are barring entry to a 21-year-old Syrian cinematographer who worked on a harrowing film about his nation’s civil war, “The White Helmets,” that has been nominated for an Academy Award.

According to a statement released by the White Helmets themselves, however, it would appear to be the Syrian government and the war they’re working in that is stopping the cinematographer -- and the head of the rescue organization -- from travelling to the U.S. for the awards show.

According to internal Trump administration correspondence seen by The Associated Press, the Department of Homeland Security decided at the last minute to block Khaled Khateeb from traveling to Los Angeles for the Oscars.

Khateeb, a volunteer with the Syrian Civil Defense (White Helmets) who also worked as a cinematographer, was scheduled to arrive Saturday in Los Angeles on a Turkish Airlines flight departing from Istanbul. But his plans were upended after U.S. officials reported finding “derogatory information” regarding Khateeb.

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Derogatory information is a broad category that can include anything from terror connections to passport irregularities. Asked for comment, a spokeswoman for the Department of Homeland Security, Gillian Christensen, said, “A valid travel document is required for travel to the United States.”

In a statement sent to CBS News on Sunday, the White Helmets said Khateeb “was not able to travel to the Oscars due to his passport being cancelled by the Syrian regime despite having been issued a U.S. visa specifically to attend the awards ceremony.”

The organization said its boss, Raed Saleh, who was already a U.S. visa holder, also could not attend as he had hoped to due to because, “the intense air strikes across the country mean he must focus on work inside Syria.”

“The White Helmets,” a 40-minute Netflix documentary, has been nominated for Best Documentary Short. If the film wins the Oscar, the award would go to director Orlando von Einsiedel and producer Joanna Natasegara. Khateeb is one of three people credited for cinematography; Franklin Dow is the film’s director of photography.

The film focuses on the rescue workers who risk their lives to save Syrians affected by civil war. Many of the group’s members have been killed by Syrian President Bashar Assad’s air forces. The group also was nominated for last year’s Nobel Peace Prize.

Syrian civil defense volunteers, known as the White Helmets, search for survivors following a reported government airstrike on the rebel-held neighborhood of Tishrin, on the northeastern outskirts of the capital Damascus, on Feb. 22, 2017. Msallam Abdalbaset/AFP/Getty Images

In a “60 Minutes” story about the rescue workers broadcast late last year, one of them, Rady Saad, told CBS’ Scott Pelley that what keeps him going is all the people who need their help.

“There’s a 50 percent chance in every operation that I’ll live and 50 percent chance that I’ll die,” Saad told Pelley. “But in the end, I’ve left my mark. I’ve left children who are going to live and complete our future.”

“The White Helmets” includes emblematic scenes of the deadly 6-year-old conflict: people digging through destroyed homes looking for survivors, at constant risk of “double tap” attacks that target first responders after they’ve arrived at the scene of a strike.

Khateeb had been issued a visa to attend the ceremony with Hollywood’s biggest stars. But Turkish authorities detained him this week, according to the internal U.S. government correspondence, and he suddenly needed a passport waiver from the United States to enter the country.

Reached by telephone, Khateeb said he was currently in Istanbul and had not been detained. He declined to speak further about his situation. And a posting on the White Helmets’ Twitter account said that “sadly,” Khateen would not be able to attend the Oscars. “Not allowed to leave Turkey because passport not issued by Damascus,” according to the tweet.

Sadly @995Khaled will not be able to attend the #Oscars2017 . Not allowed to leave Turkey because passport not issued by Damascus :(. — The White Helmets (@SyriaCivilDef) February 25, 2017

The correspondence indicated he would not receive a passport waiver. There was no explanation in the correspondence for why Turkey detained Khateeb.