The Port of Tianjin (Tianjin Gang, Chinese: 天津港; pinyin: tiānjīn gǎng), formerly known as the Port of Tanggu, is the largest port in Northern China and the main maritime gateway to Beijing. The name "Tianjin Xingang" (Chinese: 天津新港; pinyin: tiānjīn xīngǎng; literally: "Tianjin New Port"), which strictly speaking refers only to the main seaport area, is sometimes used to refer to the whole port. The port is on the western shore of the Bohai Bay, centred on the estuary of the Haihe River, 170 km southeast of Beijing and 60 km east of Tianjin city. It is the largest man-made port in mainland China, and one of the largest in the world. It covers 121 square kilometers of land surface, with over 31.9 km of quay shoreline and 151 production berths at the end of 2010. Tianjin Port handled 500 million tonnes of cargo and 13 million TEU of containers in 2013, making it the world's fourth largest port by throughput tonnage and the ninth in container throughput. The port trades with more than 600 ports in 180 countries and territories around the world. It is served by over 115 regular container lines. Run by 60 liner companies, including all the top 20 liners. Expansion in the last two decades has been enormous, going from 30 million tonnes of cargo and 490,000 TEU in 1993 to well beyond 400 million tonnes and 10 million TEU in 2012. Capacity is still increasing at a high rate, with 550–600 Mt of throughput capacity expected by 2015. The port is part of the Binhai New Area district of Tianjin Municipality, the main special economic zone of northern China, and it lies directly east of the TEDA. The Port of Tianjin is at the core of the ambitious development program of the BNA and, as part of that plan, the port aims to become the primary logistics and shipping hub of North China. On 12 August 2015, at least two explosions within 30 seconds of each other occurred at a container storage station at the Port of Tianjin in the Binhai New Area of Tianjin, China. The cause of the explosions was not immediately known, but initial reports pointed to an industrial accident. Chinese state media said that at least the initial blast was from unknown hazardous materials in shipping containers at a plant warehouse owned by Ruihai Logistics, a firm specializing in handling hazardous materials.