AKIPRESS.COM - The North Caspian Operating Company consortium developing Kashagan oilfield said the result of a probe into a toxic gas leak there was now expected in the second quarter, extending the closure of one of the world's biggest oil fields.

"The results of these investigations are expected in March/June 2014," a consortium spokesman said in written comments to Reuters. It remained unclear when crude output would restart after the project was halted by sour gas leaks shortly after start-up in September, but the delay was likely to unsettle further Kazakh authorities who have already sued the consortium for 134 billion tenge ($737 million) for ecological damage.

The consortium said last week it would challenge the fine, potentially raising tensions with a government, which in recent years has become more assertive dealing with foreign investors and has used legal action as leverage to increase participation in some large-scale energy projects. Production at the Caspian Sea field, the world's biggest oil find in 35 years, was halted in early October after gas leaks were detected in its pipeline network.

Kashagan recoverable reserves are estimated at 9 billion to 13 billion barrels of oil. The North Caspian Operating Company (NCOC) consortium, led by Exxon Mobil, Royal Dutch Shell, Total , Eni and Kazakh state oil firm KazMunaiGas, had to achieve a "commercial output" level of 75,000 barrels per day in October to meet its contractual obligations.