The incident follows the guilty plea two months ago of a Disney employee who was trying to sell early access to the company's quarterly results.
(Disney is the parent company of the ABC television network and 6abc.)
Trading in Disney's stock was in a tight range until about 3:29 p.m. Eastern time on Thursday - about half an hour before the entertainment company that owns ESPN, Marvel Entertainment and Pixar was scheduled to release its results.
The shares then plunged $1.81, or 4.9 percent, to $35.39 by 3:33 p.m., before popping back up slightly. The company news release was issued at 3:44 p.m.,16 minutes earlier than normal. Trading volume in Disney was 37.7 million shares by the end of the day, more than three times the average.
"We are aware that information regarding our fourth-quarter earnings became available ahead of its formal release and we are investigating how this occurred," Disney's senior vice president of investor relations, Lowell Singer, told analysts on a conference call. "We do regret any confusion caused by this incident."
Analysts said they were puzzled at the leak.
"It was bizarre and unfortunate," said Michael Nathanson, an analyst with Nomura.
In September, Bonnie Hoxie, a secretary to Disney's head of corporate communications, pleaded guilty in a federal court in New York to conspiracy to commit securities fraud for trying to sell access to the company's quarterly earnings ahead of their release.
A Disney spokesman declined to comment further on the company's initial findings.
The company said in its release that net income in the three months to Oct. 2 fell 7 percent to $835 million, or 43 cents per share, from $895 million, or 47 cents per share, a year earlier. Results were hurt by the shift of some revenue for ESPN to the third quarter and one fewer week in the quarter than a year ago.
Factoring out one-time items, adjusted earnings came to 45 cents per share, down from 46 cents a year ago and a penny below the forecast of analysts polled by Thomson Reuters.
Revenue fell 1 percent to $9.74 billion from $9.87 billion a year ago. That also fell short of forecasts of $9.94 billion.
Advertising revenue rose at ESPN and ABC but the one fewer week tamped down the results. When accounting for the discrepancies, ad revenue at ESPN was up 22 percent, while ad revenue at ABC was up 26 percent. Operating profit at the ABC broadcasting unit jumped to $147 million from $2 million, helped by lower programming costs in prime-time, during the day and in news production.
Parks and resorts revenue fell 1 percent as fewer people closed on Disney Vacation Club properties and domestic parks attendance fell 6 percent. Accounting for the one fewer week, the company said domestic attendance was up 1 percent.
The movie studio's revenue rose 6 percent, driven by international ticket sales to "Toy Story 3," which came out in mid-June and topped $1 billion in worldwide ticket sales. Disney recently bought back control of the marketing of Marvel-made movies from Viacom Inc.'s Paramount Pictures, starting with "The Avengers" in 2012.
Losses continued at its interactive media unit, which houses its console games, websites and its recently acquired social game developer Playdom.
Chief Executive Bob Iger said Disney recently shook up management of the division, partially to invest less on console games and more on social and mobile games and on Web delivery of its content.
"I would be disappointed if we continue to lose significant amounts of money in those businesses and if we do, I would imagine we will have to redirect in some form," he said.
In aftermarket trading, shares gained 62 cents, or 1.7 percent, to $36.55, after closing down $1.06, or 2.9 percent, at $35.93.