A Beijing subway train derailed and two of its coaches ran onto a field during a trial run on a new section of track yesterday. The train is part of Line 4, which runs north to south and is operated by the Beijing MTR Corporation, partly owned by Hong Kong's MTR Corporation. The incident came during tests on an overground section of an extension. The train failed to halt in time and two coaches went off the rails and onto the field. Two cranes were used to remove the coaches, according to the website of The Beijing News . The operator said on its official Weibo account that it was investigating the cause of the incident, and that services remained unaffected. A spokeswoman for the Hong Kong MTR said: "We are concerned about what has happened and will follow up with Beijing MTR Corporation." The scene was cleared about five hours later, the operator said. Beijing MTR Corp was jointly established in 2006 by Beijing Infrastructure Investment, Beijing Capital Group and Hong Kong's MTR Corp. Some internet users questioning whether human error was involved. "I hope that they can find out the problem during the trial and fix it as soon as possible," one person said.