Was it intentional or a real mistake? General Motors Corp. blamed "human error" for the premature release yesterday of production model photos of the Chevrolet Volt — but others think the release was planned to build hype.

As many as 10 photos of what appears to be the production version of the new Volt — the automaker's much-anticipated, yet little-seen, extended-range electric vehicle — were posted on GM's media web site and quickly picked up by bloggers.

Chevrolet spokesman Terry Rhadigan told the Detroit News that it "was not intentional." He said "those were put up in error and taken down quickly thereafter."

The pictures appeared a week ahead of the automaker's 100th anniversary celebration, during which the Volt is expected to be officially unveiled.

The Detroit News said the blogger who found the photos Monday before they were taken down suspects the release was a publicity move by the automaker.

"I think they're getting very good at playing the game of public relations," said Marty Padgett, editor of thecarconnection.com. "Everyone is interested (in the Volt), so why not let some teases float out there?"

The photos featured GM engineers and officials, including Vice Chairman Bob Lutz, kneeling, leaning and posing with the Volt.

The car has deviated substantially from the concept that appeared in Detroit, looking much more streamlined and more like a real car.

GM has said it plans to begin production of the Volt in late 2010, but that the final look would be revealed in September.

The Volt will operate like a plug-in hybrid, rechargeable via a standard 110-volt outlet and able to travel up to 40 miles on electric power alone. The car also will have a gas engine that powers a generator to recharge the battery and keep the vehicle running when its lithium-ion battery pack runs low on power.