million tons of coal reserves but in 2013 Rio Tinto downgraded these reserve estimates and noted that "...the development of infrastructure to support the coal assets is more challenging than Rio Tinto originally anticipated..." The Revuboè Mine project was another Moatize Basin coalfield mine. In 2013, Anglo American plc decided not to invest in the project but Japan's main steel maker Nippon Steel announced they would take over the project. Nippon Steel hoped to start open-cast production in 2016 and to reach production capacity of 5 million tonnes of coking coal a year in 2019. However, development of the Moatize basin coalfield depended crucially on the rehabilitation of the railway from Beira to Tete, and the construction of a maritime export terminal at Beira. Total costs of the project were estimated to be $2 billion. RICON, an Indian consortium of Ircon International and Rail India Technical and Economic Service, had been contracted to rebuild and run from Beira to Tete a 650-kilometer rail line which would link the Moatize basin coalfield with the Port of Beira. Rehabilitation was originally expected to be completed in early 2009. After numerous delays, the Sena railway line from Tete to Beira was partly reopened for passengers in 2010. RICON missed deadlines and had quality control issues, so, in December 2011, CFM, the Mozambique Ports and Railways authority, took over control of the Beira rail system. The reconstruction of the freight line was restarted in March 2012 but the work was still not finished by February 2013 In 2012 it was reported that coal exports had to be transported to Beira by a combination of truck and rail. Since Beira port was shallow, the coal had to be transported by barge out to larger vessels off the coast. In early 2013 floods prevented parts of the railway line from operating, coal stocks piled up and some coal mines had to stop production. In April 2013, three coal mining companies were reported to be building or planning to build their own railway lines to export their coal, possibly through Malawi to the deep water port of Nacala. Natural gas In 2010–2011, Anadarko Petroleum and Eni discovered the Mamba South gas field, recoverable reserves of 4,200 billion cubic metres (150 trillion cubic feet) of natural gas in the Rovuma Basin, off the coast of northern Cabo Delgado Province. Once developed, this could make Mozambique one of the