TOKYO, Japan (CNN) -- The case of a Tennessee man jailed in Japan for trying to snatch back his children from his ex-wife is not as clear-cut as it's been made out to be, authorities here said Wednesday.
The father, Christopher Savoie, apparently became a naturalized Japanese citizen four years ago, listing a permanent address in Tokyo, they said.
And while he and his ex-wife -- a Japanese native, Noriko -- divorced in Tennessee, the two never annulled their marriage in Japan, officials here said.
Also, the two children at the center of the case hold Japanese passports, they said.
The police revelations add a new twist to the case -- seemingly turning it from an international abduction to a local child custody dispute.
"His chances of getting his children back home to the States, I think, are pretty slim right now," Jeremy Morley, Savoie's lawyer in the United States, told CNN's "AC 360" on Tuesday night.
"We're getting this in the hands of Interpol. We're putting the pressure," he added. "We want diplomatic pressure. We want the United States government to act strongly."
Savoie was arrested Monday when he snatched his two children -- 8-year-old Isaac and 6-year-old Rebecca -- as his ex-wife was walking them to school in Fukuoka, about 686 miles (1,100 km) southwest of the capital, Tokyo.
He headed for the U.S. consulate in that city to try to obtain passports for them, authorities said. But Japanese police, alerted by Savoie's ex-wife, arrested him.
U.S. State Department spokesman P.J. Crowley said Wednesday, "We have paid a consular visit on Mr. Savoie and we stand ready to help him in any way that we can."
"Obviously, this is a very difficult issue," he said. "... The United States and Japan have an important partnership but on this particular issue, the issue of ... abduction, we have different points of view."
Japanese authorities said Wednesday that Savoie was eating well and was staying in a jail cell by himself.
He will be held for 10 days while prosecutors sort out the details of the case.
"I know he had to go to the hospital for blood pressure issues," his current wife, Amy Savoie, told "AC 360." "The gentleman from the consulate was able to contact me this morning, and he confirmed that Christopher had gone to the hospital. The first night he needed medication for his high blood pressure."
Savoie was married to Noriko until January. The family lived in Franklin, Tennessee.
After their divorce, the ex-wife agreed to live in Franklin to be close to the children, taking them to Japan for summer vacations.
In March, Savoie requested a restraining order to prevent his wife from taking the children to Japan, fearing she would not return.
"I was on a speaker phone telephone call once when she proclaimed to him, 'You have no idea what I'm capable of," said Amy Savoie. "So, yes, he had the idea."
Noriko Savoie could not be reached by CNN for comment.
On the first day that the two children were to begin school in August, Savoie learned his ex-wife had fled with them to Japan.
After the abduction, Savoie filed for and received full custody of the children. And Franklin police issued an arrest warrant for his ex-wife.
But Japan is not a party to a 1980 Hague Convention on international child abduction.
"We continue to encourage Japan to join with our countries and sign the Hague Convention," Crowley said Wednesday.
Foreign parents have had little luck in regaining custody, the State Department said.
"She has committed a felony, the mother," Morley said. "It's a very serious felony. She would go to jail for serious time if she were here.
"But Japan has a different legal system and a different set of customs and ideas about custody. And their idea is that somebody who is Japanese and the mother should be entitled to have the kids and have the kids alone. The fact that they were living here is kind of irrelevant, and the fact that there's a court order here is irrelevant."
So, Savoie flew to Fukuoka to try to get back his children -- and landed himself in jail.
"These kids are the ones that are suffering," Morley said. "These kids are without their father, and their father needs to be a part of their life. It's not fair that he's been taken away from them."