Alarming intelligence about Syria's chemical weapons stockpile earlier this week had to do with the apparent loading of elements of dangerous sarin nerve gas into bombs at Syrian airfields, a senior U.S. official said.

American officials remain concerned by the Syrians' intent behind the move, though their concerns have eased in the past 48 hours since the move became public.

Concerns were raised this weekend after U.S. intelligence uncovered movements on or near Syrian airfields, the senior U.S. official said.

According to the official, the U.S. believed that Syria loaded components of sarin gas into bombs near or on those Syrian airfields.

The bombs were not loaded onto aircraft. Though it is assumed that is what the intent may have been, the official said there was no way to know for certain.

On Monday, concern over the Syrian moves led to a strong warning from President Obama to the Syrian regime led by President Bashar Assad.

"I want to make it absolutely clear to Assad and those under his command: The world is watching," he said.

"The use of chemical weapons is and would be totally unacceptable," he warned. "And if you make the tragic mistake of using these weapons, there will be consequences and you will be held accountable."

U.S officials stressed that over the past 48 hours there have not been any major movements at the chemical weapons sites that were of concern.

The concerns of U.S. officials seem to have eased in the days since Obama's warning to Syria as it appeared Assad may have gotten the message not to use the weapons.

Syrian motives for the move remain unclear. One official said there was nothing to suggest that Assad ordered the move. The official said there is speculation that it may have been a preparatory move by Syrian military officials in case an order should come for their use inside Syria.

In recent weeks, there has been an escalation of the two-year rebellion against Assad's regime.

Syria has dozens of sites that house chemical weapons including sarin, VX nerve gas and mustard gas. However, the ones adjacent to or on Syrian airfields are the ones specifically drawing the attention of American officials.