Internet traffic on the mainland and in Taiwan was shut down for hours on Saturday by the computer worm - and could wreak more havoc today when offices reopen. The Chinese National Computer Network and Information Security Administrator Centre in Beijing received reports that Internet servers were clogged from 4pm onwards, the China News Service reported. The centre, in charge of Internet security on the mainland, said the situation was 'under control' five hours later. Despite the claim, staff with a mainland Internet service provider, who asked not to be named, warned further network disruption was likely when workers went back online. The worldwide Internet traffic jam was said to be caused by a worm only the size of a small file, according to the centre. Instead of attacking individual desktop computers, the worm copied itself quickly and transmitted floods of spurious signals, disrupting hundreds of thousands of other systems worldwide. 'The worm's activities immediately flooded the pipeline and thus overwhelmed the network,' an official at the centre was quoted as saying. The Internet attack was also confirmed by the Information Industry Ministry in Beijing, but an official said it was still investigating the cause of the jam. Overseas, online shopping sites and automated bank teller machines in America and South Korea were hit. The information ministry official declined to say if there had been similar problems on the mainland.