According to the LA Times, "out of an abundance of caution" customs workers were using several types of radiation detection equipment to specifically monitor maritime and air traffic from Japan for possible contamination.
International flights are routinely screened for levels of radiation but efforts have increased and the agency plans to “adjust its detection and response protocols ... as developments warrant," according to the Times.
In Fort Worth, an international flight from Tokyo set off radiation detectors after landing in North Texas.
Sarah McDaniel with Dallas-Fort Worth Airport Public Affairs told NBC News an American Airlines flight landing from Japan at 9:15am showed low trace levels of radiation in the cargo area of the aircraft.
McDaniel reiterated there was no danger to passengers and that the aircraft is back in service.
Any cargo found to be contaminated would be denied entry, an agency official told the Times.
Travelers found with signs of radiation sickness would be referred to health authorities and treated, the Times reported.