NEW YORK (CNN/Money) - Spurned Enron investors may have months to wait before the federal government makes another high-profile arrest, even in the wake of Wednesday's guilty plea from Michael Kopper, the first direct charges brought against a former executive of the bankrupt energy trader.

"Now they'll do a thorough job with Kopper, and he'll help lead them through the documents," said former federal prosecutor Richard Martin. "At the same time I think they'll be talking to other potential targets and their counsel and see if they want to cooperate. In a couple of months, we'll see some more action."

Martin added that it will become harder for Enron executives to bargain with the government, now that Kopper has set the bar at $12 million. That was the sum Kopper agreed to return to the government as part of his plea of guilty to federal charges of conspiracy to commit money laundering and conspiracy to commit wire fraud. And for senior Enron officials like Kopper's boss, former Chief Financial Officer Andy Fastow, the government may prefer to go to trial.

Fastow has been described as the architect of the limited partnerships that allowed Enron to hide millions of dollars in off-balance-sheet debt from investors. Kopper pled guilty to Wednesday to charges that he, Fastow and others used the partnerships to misappropriate millions of dollars in undisclosed fees and illegal profits.

"I think Fastow is one of the ultimate targets. He, and Skilling, and Lay. So I'm not sure they want a plea from him," Martin said. "However, if he comes in and says, 'You've got me,' I don't think they'll say go away."

Bryan Sierra, a spokesman for the Justice Department, would not comment Thursday on the prospect of additional charges in the Enron case. Justice Department officials said Wednesday that Kopper's plea should allow them to go after $23 million from Fastow and other former Enron executives.

Though Martin, now a partner at the New York firm Heller Ehrman White & McAuliffe, says it may be months before the government makes another high-profile Enron arrest, he believes that the disbursement of the recovered funds will happen sooner.

Related stories       Enron guilty plea ahead Going after Enron execs' assets

"That could happen almost anytime," Martin said. "I suspect that that's one of the things they would want to do to reassure the public."

The SEC has not yet set a timetable for that action, according to spokesman John Heine.