Tweets from Fox Business News reporters on Wednesday were the latest indication that Dimon was still in the running for the job. But initial word from anchor Maria Bartiromo that he would "get" the job was quickly knocked down.

JPMorgan spokespeople have declined to make any official comment about the idea of Dimon joining the Trump administration since Nov. 10, when reports first surfaced that he was a contender for Treasury secretary. Dimon declined to comment through a representative on Wednesday.

A Trump transition team source told Reuters that Dimon is "pitching hard" for the Treasury role.

However, two other sources indicated that he is not interested. One said Dimon has told colleagues since Nov. 8, when Trump won the election, that he would not take the role. The three sources spoke on the condition of anonymity.

Bartiromo cited a meeting on Thursday where a decision will be made on either Dimon or Steve Mnuchin, who was Trump's campaign finance manager, as Treasury secretary. Her colleague Charles Gasparino said Dimon would only be willing to play an advisory role. Fortune reported later that Dimon has already said no.

Whatever the outcome, speculation about his departure from JPMorgan rattled some investors. Dimon has run JPMorgan for a decade and is viewed as a torchbearer for Wall Street. He does not have a clear successor.

"He is one of the best CEOs in the industry and corporate America, so if there were to be a quick departure that would be troubling," said Walter Todd, chief investment officer at Greenwood Capital Management, which owns JPMorgan shares. "It is very difficult to replace someone like him."

JPMorgan's shares closed down 2.5 percent at $77.40 on heavy volume, though much of the move came before the Treasury speculation heated up.

Although Dimon has said repeatedly and publicly that he would not want to be Treasury secretary, it is rare to reject a president-elect's request to join his Cabinet. Doing so could put JPMorgan in an awkward position, because it would then be regulated by an administration Dimon spurned.

But if Dimon did take the job, it is not clear who would step in as CEO.

Several senior executives' names have been floated in the past as potential successors, including Chief Operating Officer Matt Zames and heads of business units such as Gordon Smith, Douglas Petno and Daniel Pinto, but none has been identified by the bank or insiders as being the clear choice to take over as CEO.

(Reporting by David Henry in New York and Steve Holland in Washington; Additional reporting by Chuck Mikolajczak; Writing by Lauren Tara LaCapra; Editing by Alden Bentley and Leslie Adler)

By David Henry and Steve Holland