Another Enron Corp. energy-trading executive pleaded guilty yesterday to conspiring to manipulate electricity prices during the West Coast energy crisis two years ago.

Jeffery S. Richter, 33, the former head of Enron's short-term power-trading operation in California, also admitted lying to federal investigators last year at the outset of the investigation. He faces a maximum penalty of 10 years imprisonment and a $500,000 fine. "He is cooperating now," said Assistant U.S. Attorney Matthew J. Jacobs in San Francisco, where the investigation of Enron's trading operations is centered.

Richter's boss, former Enron trading executive Timothy N. Belden, pleaded guilty in October to similar conspiracy and fraud charges involving Enron's trades in California. Prosecutors hope that Belden can lead them to higher-ranking Enron officials who approved or were aware of the trading schemes, according to people close to the inquiry.

Richter took charge of Enron's short-term trading desk in January 2000, overseeing the company's sales of electricity to the now-bankrupt California Power Exchange, which bought electricity for the state's utilities, and to the state's power grid operators, responsible for hourly purchases to meet last-minute demands.

In one of Enron's trading strategies, named "Get Shorty," Richter and his team claimed to have made advanced purchases of electricity to meet the grid's emergency backup power demands. In fact, the advance contracts were canceled and Enron lined up cheaper power to meet the commitments, without telling the state, Richter admitted.

The profits of Richter's team shot up 1,400 percent in 2000, over the previous year's figures.

In August 2000, Belden sent an e-mail -- now in government possession -- to Richter and several others at Enron, telling them to suspend such "Get Shorty" transactions in the face of state investigations into the power crisis. The California attorney general "is in search of a smoking gun and is looking to find someone who is 'gaming' the market. I don't want to provide them with any fuel for their fire," Belden said.

Prosecutors in Houston, the Commodity Futures Trading Commission and the Federal Energy Regulatory Commission also are investigating alleged manipulation of electricity and natural gas sales and pricing information in 2000-2001 by other companies.

Michelle M. Valencia, 32, a former top energy trader at Dynegy Inc., has pleaded innocent to charges of reporting fictitious energy trades to an industry publication whose data is used in pricing power sales.

A former El Paso Corp. trader, Todd Geiger, has also pleaded innocent after being charged in December with making fictitious trading reports.

Dynegy, American Electric Power Co., CMS Energy Corp. and Williams Cos. have admitted that traders issued false pricing information.

A FERC staff report warned last month that "the potential for manipulation of energy markets remains a concern."