U.S. officials concerned over North Korea’s ‘ratcheting up of rhetoric’

Updated 8:53 AM EDT, Thu March 28, 2013

Story highlights

NEW: South Korean workers enter industrial complex despite severing of hotline

NEW: The North clears them to cross the border through another line, Yonhap says

U.S. intelligence official expresses concern about "ratcheting up of rhetoric"

The announcement follows a slew of recent th