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DENVER — A Denver federal magistrate ordered an Arvada man arrested for passport fraud and identity theft, ad to remain in federal custody until he can be transferred to North Carolina.

William Ulmer was arrested Thursday at Denver International Airport by agents with the Diplomatic Security Service.

Law enforcement sources said Ulmer was arrested as he was about to board a flight to Hawaii to celebrate his honeymoon with his new wife. Federal prosecutors said Ulmer had $2,500 cash on him when he was arrested.

The U.S. Attorney in North Carolina has charged Ulmer with five counts related to passport fraud after prosecutors say he used his brother’s passport to fly to Costa Rica in March 2009 and back to the United States on Dec. 23, 2010.

His arrival in North Carolina came 18 days after his then-girlfriend, Barbara Struncova, disappeared in Costa Rica.

The native of Czech Republic hasn’t been seen since Dec. 5, 2010. Federal prosecutors say Costa Rican investigators found blood evidence and discovered money had been withdrawn from her account the day after she went missing but haven’t determined who made the withdrawal. A body has never been found.

Ulmer’s wife insisted, other than possible passport fraud, her husband has done nothing wrong.

Former friends of Barbara Struncova are less sure. Diana Zimmerman lived in Costa Rica in 2010 and has written extensively about the disappearance of Struncova on her blog.

When told about Ulmer’s arrest for passport fraud, Zimmerman said, “I personally believe he’s guilty of a lot more than passport fraud, but I think passport fraud is a great place to start.”

FOX31 also spoke to a woman who dated Ulmer from November 2013 to April 2014 and who asked to protect her identity.

The ex-girlfriend said Ulmer admitted to her that a former girlfriend disappeared in Costa Rica but said he told her Struncova left him for another man in the middle of the night,.

“That she packed a bag and left and he never saw her again. He also told me about his passport issues,” the woman said.

FOX31 hasn’t been able to determine why Ulmer’s original passport was confiscated but his ex-girlfriend said Ulmer told her, “The reason his passport had been taken away had something to do with sex trafficking and him and some friends trying to rescue some girls out of the sex trafficking industry.”

The ex-girlfriend doesn’t believe that explanation. The U.S. Attorney in North Carolina did not return phone calls seeking clarification.

Ulmer is expected to be transferred to North Carolina later this month to face federal charges.