(AGI) Rome, Sept 21 - Volkswagen was hit by a scandal onMonday, with its shares plummeting after U.S. authoritiesaccused the German car manufacturer of having tampered withdata on pollution emissions and threatened to fine the companyup to 18 billion dollars. The Volkswagen group is accused ofhaving developed a software, which has been mounted (from 2009to 2015) on the control box of 4-cylinder diesel engines ofVolkswagen and Audi models, aimed at cheating gas emissioncontrols. Volkswagen shares plummeted 18 percent in Frankfurtafter dipping 22.2 percent to 126.35 euros per share. VWGroup's CEO announced the company has ordered an externalinquiry and said he was "deeply sorry" for having violated theUnited States' rules. The U.S. Environmental Protection Agencyhas asked to recall half a million cars and a spokesperson ofthe VW group informed that the car maker has suspended the salein the United States of the models concerned, which represent23 percent of all Volkswagen cars sold in the U.S. in the monthof August. "I can confirm that sales have been halted," said acompany spokesperson. The German car maker sold almost 240,000cars in the U.S. between January and August of this year. The German government asked car manufacturers to provideinformation on the possibility that the anti-pollution datacould also have been tampered with at home and not only in theUnited States. "We expect reliable information from the carmanufacturers so that (German authorities) can check whethercomparable manipulation has happened in Germany or Europe,"said Andreas Kubler, the spokesperson for the Ministry of theEnvironment. Sigmar Gabriel, the German Economy Minister,defined it "an ugly incident" that is causing concern for thereputation of German automakers. "That this is a bad case, Ithink is clear," Gabriel told journalists after a Germanenvironment official described the case as "blatant consumerdeception". "You will understand that we are worried that thejustifiably excellent reputation of the German car industry andin particular that of Volkswagen suffers," Gabriel added. . .