E*Trade Financial

(ETFC) - Get Report

surged as much as 18.6% on Friday despite a lack of obvious news regarding the company.

Investors were furiously buying into the online brokerage firm's stock, and volume was more than double the daily average for the company.

But despite the rise in share price, discerning the exact cause for the buying spree was a bit of a mystery. Some observers speculated that perhaps a deal was coming with

Citadel Investments

, its largest stock and debt holder. Others thought short-covering could be behind the rise in the stock price.

E*Trade has been grappling with capital issues of late. Regulators are pressing the company to raise funds as loan losses and provisioning has taken a bite out of the company.

A spokeswoman said in an email exchange that the company had "nothing to report."

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This week hasn't been uneventful for E*Trade, however. Just days ago, Citadel Investments CEO

Ken Griffin

was named to E*Trade's board of directors. He will also serve on the finance and risk committee.

Published reports also said earlier this week that Citadel is working with E*Trade on a financing deal, but no specifics were disclosed. E*Trade said during its first-quarter earnings in April that it was looking at a range of financing alternatives, including a possible debt-for-equity swap with Citadel.

Citadel, as of May 13, owned approximately 89.1 million shares, or 15.6%, of E*Trade's common stock. It also owns more than 70% of the brokerage firm's outstanding senior debt, according to a

Securities and Exchange Commission

filing on Wednesday.

The filing also reiterated that E*Trade issued common stock and notes to Citadel in November 2007 as part of an agreement to shore up the firm's balance sheet. At the time, Citadel also purchased E*Trade's asset-backed securities portfolio for $800 million, or roughly 27 cents on the dollar.

Separately, E*Trade's board of directors approved a $25,000 annual cash retainer for Griffin's directorship, the filing said.

Shares most recently fell back but were still up by 12.9% to $1.88.