Obama office evacuated in South Philly

It's going to be a long 20 days. More here.

Authorities are trying to find out who sent a threatening letter containing a suspicious substance to one of Barack Obama's South Philadelphia campaign offices.

The office at 15th and Christian streets was evacuated for less than an hour after the discovery about 5 p.m. yesterday.

Police say a volunteer brought in the mail and opened a letter that contained the unknown substance. Officials evacuated the office, took the letter outside and called police.

A hazardous-materials crew responded, but investigators say initial tests determined that it was brown sugar.

Philadelphia police Capt. Mike Gillespie called the letter "somewhat threatening in nature."