Frankfurt police arrested 31-year-old Toby Studabaker, a former U.S. Marine, in downtown Frankfurt around midday Wednesday, hours after the schoolgirl, who cannot be named for legal reasons, departed for home from the southern city of Stuttgart.
A German judge was expected to issue a detention order later Thursday, in preparation for extradition, said Hildegard Becker-Toussaint, a spokeswoman for state prosecutors in Frankfurt.
German authorities initially said they would consider whether he could be charged with any offense in Germany, but Becker-Toussaint said that is now "extremely unlikely." An extradition decision could be made within days if Studabaker chooses not to contest being sent to Britain.
Studabaker, of Constantine, Michigan, had evaded police since he and the girl, whom he met in an Internet chat room, left Britain together Saturday on a flight to Paris.
The pair spent two nights in France, but they did not overnight in Germany before Studabaker took the girl to Stuttgart airport on Wednesday morning, Becker-Toussaint said.
"He put her on the plane," she said. "By the time they arrived in Germany the episode was nearly over."
In Britain, Greater Manchester Police said they expected to speak with the girl later Thursday about her five days with Studabaker. The schoolgirl and her parents spent Wednesday night at an undisclosed location, away from the family home in Lowton, northern England, to escape media attention.
Shevaun looked happy and relaxed as she left a police station in the nearby town of Leigh with her mother and father late Wednesday.
The schoolgirl had called her parents Tuesday and then again Wednesday.
"She did make a second phone call," said Greater Manchester police Superintendent Peter Mason. "She made a phone call this morning to her parents during which she again discussed that she was well, she was not under any duress, she was not being kept against her will. However, she had already parted company with Studabaker when he was arrested."
Greater Manchester Police said Studabaker had no previous convictions.
Leo Studabaker told the British Broadcasting Corp. his brother apparently believed the girl was 18 or 19 and was "very mad when he found she had lied about her age." The two had discussed marriage, Leo Studabaker said.
His sister-in-law Sherry, Leo's wife, said Toby thought the girl was 19.
"It was a big mistake," she said. "He's through with the Internet."
Police sources said images of child pornography were discovered on Studabaker's computer during investigations into the missing pair. The sources also said they had evidence, again taken from Studabaker's computer, that the ex-Marine knew that the girl was 12, not 18 or 19, as he had claimed to relatives.