BILLINGS, Mont. (AP) — The mother of an American college student arrested in central China following an altercation with a taxi driver five weeks earlier said police are demanding the equivalent of a $7,400 "ransom" for his release.

Jennifer McLean has not been allowed to see or communicate with her 25-year-old son, Guthrie, since his Sunday arrest on charges of intentional injury to the taxi driver, she said Thursday in an email to The Associated Press.

During a June 10 fare dispute in the city of Zhengzhou, Guthrie McLean pushed the driver to the ground because the driver was roughing up his mother, who is hearing impaired, according to family friend Tom Mitchell, the Beijing bureau chief for The Financial Times, and U.S. officials.

It's unclear why McLean, 25, a senior majoring in East Asian studies at the University of Montana, was not arrested until weeks later. The Zhengzhou municipal public security bureau, when contacted by The AP, said it does not take inquiries about individual cases.

Jennifer McLean told The AP her son's actions were justified because the taxi driver was hurting her.

"He would not have ceased had my son not intervened," she said.

Offices from the U.S. Consulate in the provincial capital of Wuhan spoke with McLean Thursday at the Zhenghou #3 Detention Center. He reported no physical or mental health concerns, officials said.

"Fine is a bit of an overstatement. He is enduring," Jennifer McLean said.

Montana's U.S. senators, Democrat Jon Tester and Republican Steve Daines, called for Guthrie McLean's quick release and said they were pressing the matter with U.S. Ambassador Terry Branstad in Beijing.

Daines said he also spoke with China's ambassador to the U.S., Cui Tiankai, who pledged to relay the concerns over McLean's fate to the communist nation's leadership.

"This was a young man who stepped in to protect his deaf mother," Daines said. "I realize we are subject to the laws of China (as U.S. citizens abroad) and will respect their government, but we want to make sure there is justice here."

Tester said in a statement that he was in close contact with members of McLean's family and Chinese officials to make sure he's kept safe. The police in China have seven days from the time of his arrest to file charges, Tester's office said, based on information provided by the U.S. Embassy.

A U.S. State Department official confirmed the basic details of the case and said the agency was monitoring the situation, but declined further comment.

Jennifer McLean has been teaching in Zhengzhou, where Guthrie visited her this summer.

The altercation occurred after a cab driver refused to give her 30 yuan (about $5) in change upon returning to her residence, Mitchell said. After the driver "started to rough up Jennifer," Guthrie came out and pushed the man to the ground, he said.

Police arrived at the residence on Sunday, took Guthrie away and demanded he pay 100,000 yuan ($14,800) in compensation for knee injuries sustained by the driver or else he would have to spend three years in prison, Mitchell and Jennifer McLean said.

The price has since dropped to 50,000 yuan ($7,400), Jennifer McLean said.

Guthrie McLean has been at the University of Montana in Missoula for about two years and worked for the past year in the Department of Modern and Classical Languages and Literatures, said his boss, Olivia White.

He largely grew up in China after living in Missoula as a young child while his mother was studying at the university, said White.

"He's very kind, gentle," White said. "His mom is all he has and I do think he defended her. He's not denying that he did it. He's denying the extent of what happened."

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Associated Press writers Mead Gruver in Cheyenne, Wyoming and Matt Volz in Helena contributed to this story.

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Follow Matthew Brown on Twitter at www.twitter.com/matthewbrownap