President Barack Obama confirmed Friday that officials found explosive materials on board cargo planes in the United Kingdom and Dubai -- and that the packages were headed to the United States.

The two suspicous packages were found during a routine plane search late Thursday night, prompting national security officials to alert Obama to a "potential terrorist threat."

An international terrorism investigation is now underway.

"The president directed U.S. intelligence and law enforcement agencies, and the Department of Homeland Security, to take steps to ensure the safety and security of the American people, and to determine whether these threats are a part of any additional terrorist plotting," the White House said in a statement Friday.

Click play for more insight on the terror threat in Yemen with CBN News Terrorism Analyst Erick Stakelbeck.

The packages were sent via UPS and came from Yemen -- home to the al Qaeda branch that tried to bomb a U.S.-bound airliner last Christmas.

The U.K. package contained a toner cartridge with wires and powder.  Dubai officials also said they'd intercepted an "explosive device."

A Sept. 23 bulletin from the Department of Homeland Security warned that terrorists wanted to mail chemical and biological materials as part of an attack against the country.  The U.S. has issued similar warnings before.

Searches were also conducted on cargo planes in New York City, Newark, N.J., and Philadelphia. No devices were found on those planes.