Apple Inc (AAPL.O) shares tumbled in early trading on Monday, briefly suffering their largest price drop in at least three months on an unusual spike in volume.

Large sell orders were seen at 9:51 a.m. EST, with more than 6.7 million shares trading in a one-minute stretch, the heaviest minute of trading in Apple since Oct. 29.

The stock lost over 3 percent in that minute, falling as much as 6.4 percent to $111.27, and was last down 2.7 percent to $115.66.

The cause of the decline was not yet clear. Morgan Stanley strategists dropped Apple's weighting in their strategic portfolio to 3 percent from 4 percent in an equity outlook note released Monday, but traders said the swiftness of the decline was too dramatic to be attributed solely to the note, which was released before trading opened.

At the day's low, Apple had lost more than $35 billion in market value, as traders pointed to high-speed algorithmic trading programs as a potential culprit.

"Maybe it was the Morgan Stanley news that kind of stimulated the event, but certainly not enough to move a stock $35 billion," said Joe Saluzzi, co-manager of trading at Themis Trading in Chatham, New Jersey.

"What that is called is evaporation of liquidity, liquidity that was never there in the first place and it's a typical maneuver that goes on in the fragmented stock market we have now," said Saluzzi.