HELENA -- On a 5-0 vote, the state Public Service Commission on Thursday authorized Attorney General Mike McGrath to investigate whether Montana consumers were harmed financially by electricity market manipulations that artificially raised prices in the West in 2000 and 2001.

McGrath filed a request for the investigation with the PSC on July 1, but it was not acted upon until this week. The commission directed its staff to prepare an order that will be voted on next week to formally clear the way for the Justice Department investigation.

In July, McGrath filed a lawsuit in state District Court against 15 out-of-state energy companies he accused of ripping off millions of dollars from Montana consumers and businesses by illegal manipulating electricity and natural gas markets over the two years. That lawsuit relies heavily on the Federal Energy Regulatory Commission investigation that concluded there was manipulation of the California energy market. His lawsuit remains on hold, pending the PSC investigation.

The PSC finally authorized the investigation Thursday, initially limiting to electricity from the western states power grid.

McGrath said later he was pleased by the PSC decision after personally pleading for the agency's support on Wednesday.

''We're off and running, and we've already done some preliminary things based on the findings made by FERC," said McGrath, the state's chief legal and law enforcement officer. ''It's good news, and we're anxious to see where it comes out."

The commission's decision to OK the investigation came after extensive debate over two days and against the recommendation of its chief lawyer, Robin McHugh, who said it exceeded the agency's legal powers.

Commissioner Matt Brainard, R-Florence, also expressed his doubts about the scope of the investigation and whether the PSC had the authority to approve it, but ultimately went along with it.

''I just want to make sure everything is done so it doesn't blow up on us," Brainard said. ''I'm not keen on deputizing a bunch of people and having them run around in jackboots."

Brainard said he wants the commission ''to run a tight ship and run a tight investigation" and ''not get taken off on a wild goose chase."

Other commissioners expressed confidence in the investigation.

''We can have a very focused look at the players that were involved and whether any of these players were identified by the FERC as engaged in fraudulent actions," said Commissioner Tom Schneider, D-Helena. ''So I think it can focus on the damage that may have occurred to customers by bad actors."

PSC Chairman Bob Rowe, D-Missoula, added, ''The information coming out of an investigation is, by itself, potentially very valuable."

McGrath said FERC already has determined the western energy market was illegally manipulated and yielded artificially high prices, he said.

''Our role is to try and determine how that impacted Montana consumers - not only residential but those who exercised their choice and bought power on the common market," he said. They included some major industries, some residential consumers, schools, local governments and the Flathead Electric Cooperative, he said.

McGrath said the Justice Department will use some national consultants who have worked primarily with the state of Nevada on the same issue.

Commissioner Greg Jergeson, D-Chinook, had pushed for the investigation to examine at natural gas markets as well as electricity from the Midwest, but agreed to initially limit it to electricity from the West.

''Let's face it, Enron was acting all over the country," he said of the Houston energy trading firm whose top executives have been charged with manipulating the markets.