A Grafton doctor who is a naturalized U.S. citizen from Nigeria says he and his ailing sister were physically and verbally abused by officials at the Pembina port of entry.

Dr. Joshua Omotunde, who works at Unity Medical Center in Grafton, said he and his 71-year-old sister were handcuffed and dragged and he was struck by officers at the border crossing when he and his sister were returning from Winnipeg, Manitoba, earlier this month.

"I am very much convinced that the whole event occurred basically because I am an African-American who was unfortunate to be traveling on that lonely and rough road that night," Omotunde wrote in a letter to North Dakota's congressional delegation.

"It's really an outrageous situation, that any U.S. citizen would be treated like that," said Mark Schneider, of Fargo, Omotunde's attorney.

"My client is a medical doctor, practicing in Grafton for the last 10 years. He's an American citizen, he's a major in the U.S. Army Reserve, and he was with his 71-year-old, diabetic, really sick sister," Schneider said.

Willie Hicks, a spokesman for the federal agencies, said the allegations are being taken seriously.

"ICE (Immigrations and Customs Enforcement) and CBP (Customs and Border Patrol) have an investigation going to find out what happened," he said

In a March 20 letter to Sens. Kent Conrad and Byron Dorgan and Rep. Earl Pomeroy, D-N.D., Omotunde outlined what he said occurred the night he tried to return to North Dakota.

Omotunde said he and his sister traveled from the Winnipeg airport to the Pembina port of entry on March 1, in a blizzard. At the border crossing, Omotunde showed a passport, his sister showed an ID card, and they answered "the usual questions" about who they were and what they were doing, he said.

Faron Johnson, a supervisor at the Pembina station, said people crossing the border have to satisfy officers that they are authorized to cross the border. Johnson would not comment on Omotunde's case.

Omotunde said he and his sister waited in a small room in a garage while port personnel inspected his car. Because his sister has claustrophobia, Omotunde said, he asked the officers to leave the door cracked open or let them stand near his car.

One officer wanted them to stand outside in the blizzard, he said. When Omotunde protested, the officer ordered the others to handcuff him, he said.

"It was like a bad dream … and before I knew it about four or five officers jumped me from the back, hit my head against the wall and knocked me down and struggled to get my arms into a handcuff," Omotunde wrote in his letter.

"I knew one of them put either a boot or his knee behind my neck and another one was pulling my head back," the letter continued.

Omotunde said he and his sister were handcuffed and dragged through the snow.

He said the officers made "derogatory remarks" to him all night and talked about shooting him. They would not let him contact his family, call Unity Medical to check on patients or check on his sister, he said.

Omotunde said he agreed to give a statement to one officer because he was sure he did not do anything wrong.

"He then proceeded to inform me that from the report they gave him that I was the one who assaulted the officers," Omotunde wrote.

After hearing Omotunde's story, the officer called the situation "bizarre," Omotunde said, and he and his sister were allowed to leave with all their possessions. He was told he would not be prosecuted, but that the matter would be investigated.

No charges have been filed, Schneider said.

Omotunde and his sister drove back to Grafton. He said they remain shaken by the incident.

"I feel withdrawn. I feel sad and depressed and this, besides the headaches that I have and suffer every day on this account," he wrote. "My 71-year-old sister also has been shaken thoroughly because she thought her brother had been killed in the event."

Omotunde's immediate priority is having the matter investigated, Schneider said.

"He wants to make sure this doesn't happen against anybody else," he said.

The state's congressional delegation called for an investigation.

Pomeroy said the allegations are extremely troubling coming from Omotunde, whom he labeled a "credible individual."

"In my years here, I've not had a similar allegation of this type of inappropriate conduct of a border official. It's very much out of character of how we know things work at the border," Pomeroy said.

In a letter to Thaddeus Bingel, assistant commissioner for congressional affairs at Customs and Border Patrol, Dorgan said port personnel told him the incident was recorded by video cameras, and he asked that Bingel obtain the video cameras for use in the investigation.