"According to an anonymous complainant, as of December 2014, ISIS [the Islamic State of Iraq and Syria, IS] instructed an ISIS [IS] member, a presumed USPER [US person] in Memphis, with a direct order to blow up the Memphis-Arkansas bridge on an unknown date, activating ISIS terror cells in the United States," the FBI warning said.
IS, a jihadist group, has been fighting against the Syrian government since 2012. In June 2014, the group extended its attacks to northern parts of Iraq, declaring a caliphate on territories under its control.
The United States set up an international coalition against the militants, with some 60 nations directly or indirectly participating in airstrikes against IS in both Iraq and Syria.
Earlier in December, French police said they had dismantled an alleged underground IS cell. Earlier in the year, similar reports surfaced in the United Kingdom. In September, Australian police conducted massive raids in Sydney and Brisbane disrupting what intelligence said appeared to be an IS-orchestrated attack on Australian soil.