(CNN) -- President Barack Obama left for Camp David on Marine One Friday but, in a twist that has left some White House reporters scratching their heads, he apparently arrived at the presidential retreat by car. White House Press Secretary Jay Carney explained the decision not to land at Camp David was made in advance because of the weather. Marine One landed at an alternate site near Frederick, Maryland and the president and his daughter, Sasha, rode in a motorcade the rest of way to the compound. Because it is customary practice that the traveling press pool is included whenever the president uses a motorcade, reporters naturally wondered why the pool was not part of the trip or even informed that the president would use a motorcade ahead of time.
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NEW: In a separate incident, NORAD intercepts an aircraft in the vicinity of Camp David
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Obama left for Camp David on the presidential helicopter but apparently arrived by car
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Marine One was reportedly diverted because of bad weather
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CNN's weather team found no signs of stormy weather in the area
No other details were immediately available on the incident, which was separate from the decision to divert @placeholder.