A letter received Friday at ARCO's La Palma headquarters threatened there were toxic substances on it, but authorities later determined it was harmless, according to the FBI.
Investigators from the Orange County Sheriff's Department bomb squad, Orange County
Fire Authority and FBI responded Friday night to the offices at Orangethorpe Avenue and Valley View Street to check out the threat.
The letter will be sent to a laboratory for further examination, Laura Eimiller of the FBI said.
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Eimiller declined to reveal any more details about the letter.