Washington, Nov 7 (IANS): The US introduced new airport security measures as a result of the ongoing investigation into the last week's Russian airliner tragedy on Egypt's Sinai peninsula, the country's Homeland Security Secretary Jeh Johnson has said.

President Barack Obama cited the possibility that an explosive device aboard caused the crash the aircraft which took off from the Egyptian city of Sharm el-Sheikh en route to St. Petersburg, Efe news agency reported.

All 224 people aboard were killed in the crash of the airbus A-321.

These stepped-up measures "will supplement the US aviation security requirements currently in place at all of foreign last-point-of-departure airports, as well as the additional security enhancements I directed last summer at certain foreign locations," Johnson said.

The secretary said while there are no direct flights between the US and Sharm el-Sheikh, and while the investigation into the crash continues, "precautionary security measures" will be increased.

Johnson specified that the enhanced measures include "expanded screening applied to items on aircraft, airport assessments in conjunction with our international partners, and offers of other assistance to certain foreign airports related to aviation and airport security."

"At this time these security enhancements are intended only for certain foreign airports in the Middle East region," he said.

"While we cannot discuss the full details of our aviation security measures, or the enhancements noted on Friday, I want to assure the travelling public that the department of Homeland Security is working closely with our domestic and international partners to evaluate the cause of the crash, and will continue to take appropriate precautionary security measures," Johnson said.

The causes of the crash are being investigated and for now it was shown that the airplane suffered an explosion in midair 23 minutes after takeoff.

However, the US does not dismiss the possibility that the IS was behind the accident.