Chinese social networking websites that provide Twitter-like services have suddenly reverted to testing mode and access has been spotty amid reports of a government clampdown. Although Twitter has been banned for more than a year in China, Chinese Internet companies have been quick to fill the void, providing microblogging services that allow users to post frequent updates and follow other posters. On Wednesday, NetEase.com Inc’s microblog (t.163.com) was inaccessible. A notice said the site had been down since 7 p.m. on Tuesday and was under maintenance. Sohu.com Inc’s microblog (t.sohu.com) was also shut down for more than a day earlier in the week and all Chinese “twitters” now display the notice “in testing mode.” Company sources told Reuters that the developments were the result of tightened government controls over the new services. The Shanghai-based Oriental Morning Post cited unnamed “industry sources” as saying that the websites were under pressure from Chinese censors.