Burger King Holdings Inc
Alex Behring of 3G was not immediately available and a Burger King spokesman declined to comment.
The second-biggest U.S. hamburger chain has underperformed McDonald's Corp
The Miami-based company, which has a market capitalisation of about $2.3 billion (1.4 billion pounds), debuted as a public company in May 2006 with an initial share price of $17 (11.00 pounds).
Shares were up $2.49 (1.61 pounds) at $18.94 (12.25 pounds) in afternoon trade.
We would view this as an excellent opportunity for investors who have been in the shares to cut their losses (or take some modest gains, depending on when shares were bought), Janney Montgomery Scott analyst Mark Kalinowski said in a note.
Burger King may actually be better off as a privately held entity at this point in its history, Kalinowski added, referring to the company's strained relations with franchisees and its struggles to better compete against McDonald's, which has been expanding its share.
Begun in 1954, this would not be the first private equity takeover for Burger King. In 2002, British drinks giant Diageo
While we would not consider a transaction a foregone conclusion, we see several factors that make a buyout plausible, R.W. Baird analyst David Tarantino said in a note.
Private equity firms have become increasingly active and last month was the busiest August since 1999 in terms of the value of merger and acquisition deals struck.
A sale would give Burger King's current private equity investors a logical exit from their positions, Tarantino said.
One of the potential suitors named in press reports, British private equity firm 3i Group Plc
We can confirm that we are not in discussions with Burger King, a spokeswoman for 3i said.
Burger King last week forecast weak demand during its new fiscal year due to the U.S. economy's slow pace of recovery and government austerity programs in several European countries. The company said it was unsure how costs for key ingredients like beef would impact the company.
Its shares hit a low of $16.30 (10.55 pounds) in mid-August, but surged to $19.50 (12.62 pounds) in premarket trading on Wednesday.
In July, an affiliate of Apollo Management wrapped up its $694 million (449 million pounds) acquisition of Carl's Jr parent CKE Restaurants Inc and a Golden Gate Capital affiliate bought On the Border Mexican Grill & Cantina from Brinker International Inc
Meanwhile, chains like California Pizza Kitchen
(Reporting by Megan Davies in New York, Simon Meads in London and Lisa Baertlein in Los Angeles; Additional reporting by Krishna N. Das in Bangalore and Ben Klayman in Detroit; Editing by Dave Zimmerman, Gunna Dickson, Leslie Gevirtz)