Washington, Jan 29 (IANS/EFE): US airlines have registered more than 50 bomb threats over the past 10 days, FBI sources have told the CNN television network.

None of the threats were considered credible but the US government will continue to investigate the rise in the number of warnings, the sources said, according to a CNN report on Wednesday.

"Threats of this nature can and do result in costly responses from a multitude of law enforcement and airport entities and greatly inconvenience travellers. Individuals responsible can be prosecuted federally," an FBI spokesperson told CNN on condition of anonymity.

On Jan 17, an F-16 fighter escorted two planes that flew into the Atlanta Hartsfield-Jackson International Airport after a bomb threat was made on Twitter which the authorities thought was authentic.

The two flights, Southwest Airlines 2492 and Delta 1156, landed without incident and no suspicious material was found aboard the planes.