NEW YORK — Federal authorities are poised to level a criminal indictment against SAC Capital Advisors, the hedge fund run by billionaire Steven A. Cohen, capping a nearly decadelong insider-trading investigation into one of Wall Street’s most prominent firms.

Prosecutors and the FBI in Manhattan are expected to announce the charges in the coming days, according to people briefed on the matter, who spoke only on the condition of anonymity. The move, a rare aggressive action against a big company, could cripple SAC.

It is unclear whether SAC’s lawyers will try to settle at the last minute, although that is unlikely at this point. Cohen is not expected to be charged criminally, although authorities are still contemplating bringing charges against other employees at SAC.

While the legal deadline for filing some insider-trading charges might have already passed, authorities are planning to navigate around that requirement by filing a broader criminal-conspiracy case against SAC, these people said.

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As long as one of the trades cited in the case took place in the past five years — and some did — then the government has the power to sweep in older trades to highlight a continuing scheme.

Representatives for the government and SAC declined to comment.

The indictment would come on the heels of the Securities and Exchange Commission’s (SEC) filing a civil action last week. It accused Cohen of failing to supervise employees suspected of insider trading. Those employees, Mathew Martoma and Michael S. Steinberg, had been charged with criminal wrongdoing.

In its order, the SEC cited a 2008 email forwarded to Cohen in which an SAC analyst explicitly stated that he had a “2nd hand read from someone at” computer-maker Dell, a source who provided financial information about the company before its earnings announcement. Minutes after receiving the email, Cohen sold his entire Dell position, the SEC said.

In a 46-page document responding to the SEC’s charges, Cohen’s lawyers said he did not see the email.

Martoma, 39, and Steinberg, 40, have each pleaded not guilty to criminal insider-trading charges and face separate trials in November.