The Latest on the slaying of British lawmaker Jo Cox (all times local):

9:55 a.m.

A U.S. civil rights group says a man arrested over the slaying of a British lawmaker had links to an American white supremacist organization.

The Southern Poverty Law Center says it has records showing Thomas Mair was a supporter of the National Alliance. The center says Friday that Mair purchased a manual from the group in 1999 that included instructions on how to build a pistol.

Mair, 52, was arrested Thursday on suspicion of killing Jo Cox, who was shot and stabbed in a daylight attack in her northern England constituency. Cox was a Labour Party lawmaker and former aid worker who had championed the cause of Syrian refugees.

The National Alliance was founded by William Pierce, who died in 2002. His book "The Turner Diaries" has been called a grisly blueprint for a bloody race war. Timothy McVeigh based the 1995 bombing of the Oklahoma City federal building, which killed 168 people, on a truck-bombing described in the book.

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9:30 a.m.

Campaigning in the referendum on Britain's membership in the European Union remains suspended as Britain mourns the killing of Labour Party legislator Jo Cox.

It is not yet clear when campaigning will resume ahead of the vital June 23 vote on whether Britain should remain in the 28-nation bloc.

There were tributes to the 41-year-old Cox across much of Britain Friday.

She was shot to death Thursday afternoon in her constituency near Leeds in northern England. A 52-year-old man has been arrested but has not been charged. He has been named locally as Tommy Mair.

West Yorkshire Police have not offered a motive for the slaying.