Linn Energy LLC is offering approximately $600 million more to buy Berry Petroleum Co., under a merger deal announced Monday by both companies.

Linn, based in Houston, is one of the nation’s top-15 oil and natural gas producers. Berry owns the Placerita oilfield (off of Sierra Highway in Newhall) and bigger oil properties in Kern County, West Texas and Utah.

Under the original deal, Berry shareholders were to receive 1.25 shares of Linn affiliate LinnCo. Under the new deal, shareholders would receive 1.68 shares for each Berry share – a total increase of more than half a billion dollars, to $4.9 billion.

Berry’s share prices jumped about 11 percent on Monday’s news and retreated slightly Tuesday.

The original deal was supposed to have been completed by June 30, but it didn’t happen because it requires SEC approval and Linn has been sidetracked by an SEC inquiry into its hedging strategy. The new agreement, which has been approved by both companies’ boards, extends the completion date to Jan. 31, 2014.

“The boards and management teams of Linn and Berry remain committed to completing this merger,” the companies’ CEOs said in a joint statement. “We continue to believe that, upon completion, this transaction will create tremendous value for Linn Energy, LinnCo and Berry investors.”

Linn CEO Mark E. Ellis justified the higher offer by saying that since his company first started planning the takeover, Berry’s operations “have consistently outperformed expectations, which is evidenced by their recent third quarter 2013 results.”

Berry has been ramping up its oil production all year. It brought 41,413 daily barrels of oil and  natural gas to market during the third quarter, a 14 percent increase over the same period in 2012.

One third-quarter highlight was the drilling of 18 new oil wells in California, including nine at Placerita.