FRANKFURT - Germany’s motor vehicle regulator will run tests on more than 50 models of 23 German and foreign car brands on suspicion of further manipulation of nitrogen oxides emissions from diesel engines, it said on Wednesday.   The Kraftfahrt-Bundesamt (KBA) regulator said the tests were triggered by Volkswagen’s admission it had rigged such tests but also cited “verified indications from third parties regarding unusual pollutants emissions”.   “Since the end of September KBA has been investigating whether further manipulation of emissions, of nitrogen oxides in particular, is taking place in the market,” KBA said in a statement.   The watchdog said it has been comparing readings in a test setting with those from portable meters in real-life tests and two-thirds of the measurements had already been taken. Germany’s Transport Minister Alexander Dobrindt said in a newspaper interview over the weekend that diesel vehicles, including those from foreign manufacturers, would be subjected to strict checks.   VW admitted in September to cheating tests for emissions of nitrogen oxides and the scandal widened with VW’s revelation last week that it had also understated carbon dioxide emissions.