By Ahmed Mohamed Hassan

CAIRO (Reuters) - Two employees of Egypt's Sharm al-Sheikh airport have been detained for questioning over the crash of a Russian airliner that killed all 224 people aboard, two security officials and an airport employee said on Tuesday

"Seventeen people are being held; two of them are suspected of helping whoever planted the bomb on the plane at Sharm al-Sheikh airport," said one of the security officials, both of whom declined to be named.

The second security official said CCTV footage showed a baggage handler carrying a suitcase from an airport building to another man, who was loading luggage onto the doomed airliner from beneath the plane on the runway.

An employee at the airport media department, who also preferred to remain anonymous, confirmed two members of the ground crew had been detained for questioning on Monday night.

Egyptian Interior Minister Magdi Abdel Ghaffar said there were no arrests. "This news is incorrect, it was probably reported because of the strict inspection checks that all airport workers are undergoing," he said.

Russia's FSB security service said on Tuesday it was certain a bomb had brought down the Airbus jet on Oct. 31, joining Britain and the United States in reaching that conclusion.

Egypt has not yet formally confirmed that a bomb was responsible, saying it wants to await the completion of all investigations.

It was not immediately clear what role the employees said by security sources to have been detained had at Sharm al-Sheikh airport, which is Egypt's third-busiest, handling a vast number of charter and budget flights for tourists seeking sea and sun in the southern Sinai peninsula.

Separately, other sources at the airport said security forces were searching for two employees suspected of leaving a baggage-scanning machine unattended for a period of time while passengers were boarding the doomed Russian plane.

CCTV footage was being examined to confirm what happened.

Story continues

The sources said investigators had questioned all airport staff involved with handling the Russian jet, its passengers and bags after the crash. No arrests had been made in the search for the two employees who were believed to have stepped away from the baggage-scanning machine.

Since the disaster, many flights to and from Sharm al-Sheikh have been suspended, raising concern that Egypt's $7 billion tourism industry, still a pillar of the economy despite having fallen sharply in recent years, will be further ravaged.

Alexander Bortnikov, the head of Russia's FSB, said the conclusion of Russian investigators was that a homemade bomb containing around 1 kg (2 lbs) of TNT had detonated during the flight, causing the plane to break up in mid-air.

"We can unequivocally say it was a terrorist act," he said.

Egyptian ministers were meeting in Sharm al-Sheikh on Tuesday, with a news conference expected later in the day.

(Reporting by Cairo bureau; Writing by Luke Baker; Editing by Michael Georgy and Mark Heinrich)