Nearly 700 runners had shown up at the Oval Friday night for the Halifax Relay for Life when someone called 911 and made threats that alluded to the Boston Marathon bombings, the Canadian Broadcasting Corp. reported.
Halifax Regional Police said they quickly tracked the call to a payphone but couldn't find the suspect.
"It is disheartening that someone would make such threats and affect a charity event in our community which many people enjoy every year," Staff Sgt. Reid McCoombs said in a statement.
The event has raised more than $150,000 for the Canadian Cancer Society.
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