updated 6/26/2009 8:23:15 PM ET 2009-06-27T00:23:15

One of two Illinois brothers charged in a 2004 bombing that injured a black city official in a Phoenix suburb had ties to white supremacist groups and once was deported from Canada because of his activities.

Groups that track hate groups describe Dennis Mahon, 58, as a prominent player in white supremacist groups for 15 to 20 years. Less is known about his twin brother, Daniel Mahon, but he also belonged to such groups, federal officials said Friday.

The brothers are charged with conspiracy to damage buildings and property by means of explosives. They were arrested Thursday at their home in Davis Junction, Ill., where authorities say they found assault weapons, hundreds of rounds of ammunition and white supremacist material.

The brothers pleaded not guilty and were in the custody of federal authorities in Illinois. They are scheduled for an extradition hearing Wednesday.

Authorities didn't know if the brothers had attorneys.

On Feb. 26, 2004, a package detonated in the hands of Don Logan, Scottsdale's diversity director at the time, in the city's Human Resources Complex. The explosion injured his hand and arm and hurt a secretary.

Dennis Mahon led the Ku Klux Klan in Oklahoma in 1991, recruited neo-Nazis and skinheads in the former East Germany, and later joined the White Aryan Resistance, according to the Alabama-based Southern Poverty Law Center.

'One of the scarier guys around'
"Dennis Mahon in the '90s was one of the scarier guys around," said Mark Potok, director of the center's Intelligence Project.

In 1993, Dennis Mahon was deported from Canada after an immigration official ruled he would likely break the law while there. Officials there had obtained a videotape of a 1991 speech Mahon gave to the neo-Nazi Heritage Front in Toronto and similar tapes from Germany and the U.S.

Daniel Mahon was a member of the White Aryan Resistance and a recruiter for the KKK, according to the Southern Poverty Law Center.

A federal indictment unsealed Thursday says Mahon participated in the construction of the bomb, disguising it in a cardboard box addressed to Logan, an ombudsman for city employees and citizens on issues including racial and sex discrimination. The explosion forced the evacuation of 25 people in the building.

Dennis Mahon also is charged with malicious damage of a building by means of explosive and distribution of information related to explosives, according to the indictment.

Authorities said the Wednesday arrest of Robert Neil Joos, 56, of Missouri, arose from the bombing. He is charged with being a felon in possession of firearms but is not charged in the bombing.

Dennis Mahon made a call to a cell phone registered to Joos the morning of the bombing, according to an affidavit filed supporting the arrest.

A public defender assigned to his case did not immediately return a call for comment Friday afternoon.

More arrests could come
Federal agents also raided the Indiana home of Tom Metzger, president of the White Aryan Resistance, as part of their investigation into the bombing, said Special Agent Tom Mangan, a spokesman for the Bureau of Alcohol, Tobacco, Firearms and Explosives. Authorities removed computers and other items from Metzger's house but did not arrest him.

A call to Metzger went unanswered, and he did not have an answering machine.

Mangan said authorities are looking into other members of white supremacist groups who associated with the Mahon brothers, and that more arrests could come in the bombing case.

More on: White Aryan Resistance

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