WINNIPEG -- A Winnipeg man says U.S. border officials detained him and his family for seven hours and never told him why.

Abdelkrim Boulhout says his family was headed to Grand Forks, N.D., to celebrate their youngest son's first birthday and go to a waterpark.

They arrived at the Pembina border crossing on Saturday and were ushered inside while Boulhout says he was questioned for seven hours.

Boulhout, who was born in Algeria but has been a Canadian citizen since 1992, says border officials eventually told him he could go back to Canada but asked him to sign a document stating he understood why they denied him entry.

He says officials didn't list any reasons on the form, but he agreed to sign it because they threatened to handcuff him and put him in a cell if he refused.

U.S. Customs and Border Protection officials say they're looking into what happened.

"I never had any trouble with the law, ever before," Bulhout told CTV, noting that a criminal record check he obtained for his work at CP Rail came back clean.

The family said the children were hungry and no one offered them food.

Youzef Boulhout, 5, said he thought his father was in jail and Mohemd Boulhout, 8, said the border guard asked why he wanted to come to the U.S.

"They said why are you coming to this country? You could go to Canada to the other waterpark," Mohemd said.

The U.S. Customs and Border Protection website lists many reasons why people may be denied entry.

It says people who feel they've been wrongly denied entry can file a claim with the Department of Homeland Security Traveler Redress Inquiry Program.