Traders were focusing on tech stocks and energy companies in the extra session Monday, but the momentum from regular trading didn't seem to be spilling over.

Volume was moderate, with around 3.3 million shares changing hands among the top-20 Instinet volume movers in the first 45 minutes of trading.

Calpine ( CPN), the volume leader, was climbing 1.8% to $6.95. In regular trading, Calpine lost almost 4%, but still finished well above its worst level of the day, as investors worried about the energy company's long-term power contracts with California.

Flextronics ( FLEX) was one of the late session's biggest losers, dropping 3.7% to $15.40 after the contract manufacturer's chief executive said on a conference call that earnings for the fourth quarter would be lower than expected. Shares of rival Sanmina-SCI ( SANM) were dropping 2.7% to $10.41.

Sprint PCS ( PCS) was losing 4.5% to $9, after gaining 14.2% in regular action. AT&T ( T) was slipping 0.6% to $15.40.

As usual, widely held tech issues were among the volume leaders. Sun Micro ( SUNW) was inching down 0.2% at $8.85, and Microsoft ( MSFT) was off 0.1% at $59.04.

Cisco ( CSCO) was flat, Dell ( DELL) was down 0.2% and Intel ( INTC) was up 0.4%.