A University of Montana student is in custody in China after an altercation with a cab driver, the student's mother tells CBS Missoula, Montana affiliate KPAX-TV.

Jennifer McLean says her son, Guthrie McLean, is accused of assaulting the taxi driver -- but says it happened after the driver attacked her.

Local police in China refused to confirm or deny to CBS News that Guthrie is being held.

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According to KPAX, Guthrie McLean essentially grew up in China, where Jennifer teaches English. But in recent years, Guthrie has been enrolled at the University of Montana.

In late May, Jennifer tells KPAX, he went to China to visit her in Zhengzhou, southwest of Beijing.

As Jennifer tells it, on June 10, she took a cab home. The fare came to 70 Renminbi, or $10.36. Jennifer paid with a 100 Renminbi note and, says family friend and Beijing journalist Tom Mitchell, that's when the trouble began.

"He basically refused to give her the proper change," said Mitchell. "There then was a bit of an argument and the taxi driver started to rough Jennifer up. So, she describes him pushing and shoving her, grabbing her bags; she was very scared. She was able to call Guthrie and he saw what was happening. He pulled the taxi driver off her, threw him to the ground, and end of story. Or so it seemed."

Five weeks later, Zhengzhou police came looking for Guthrie McLean. The cab driver had alleged serious bodily injury, and the UM student was asked to pay 100,000 Renminbi (roughly $14,800) as a settlement. Unable to pay, McLean was taken into custody and given an arrest notice, but no formal charges were brought.

He's been held since Sunday on bond of 50,000 Renminbi (some $7,300), Jennifer tells CBS News.

"What that allows them to do is then transfer him to a detention center, sort of a holding facility while they decide along with a prosecutor whether or not to formally charge Guthrie," Mitchell explains.

Those agencies have approximately 30 days to decide whether or not to press charges, during which McLean has to stay behind bars. If no charges are lodged, he will be free to go, but if the case is brought to trial, Guthrie could remain in custody for some time, Mitchell says.

"You could end up actually sitting in the detention center for the better part of a year waiting for the police and prosecutors to finish their investigation, at which time it goes to trial," Mitchell says.

Jennifer McLean says she's reached out to the U.S. Embassy in Beijing, but Zhengzhou falls under the Henan Consulate's jurisdiction. Efforts are being made to get help from the Consulate.

MTN News reached out to the offices of Montana Senators Jon Tester and Steve Daines for comment.

"Senator Tester's office was informed of this incident on Monday, and within minutes contacted the State Department and the U.S. Embassy in China. Senator Tester is working closely and urgently with officials here and abroad to secure Mr. McLean's quick release and to safely resolve this matter," Sen. Tester said in a statement.

Sen. Daines' office told MTN News he has reached out to the U.S. State Department, the U.S. Embassy and the Chinese Embassy.

Jennifer McLean told CBS News she's been told U.S. State Department personnel might attempt to visit Guthrie Friday.