U.S. investigators probing Mercedes maker Daimler have found that its cars were equipped with software which may have help them to pass diesel emissions tests, a German newspaper reported on Sunday, citing confidential documents. There has been growing scrutiny of diesel vehicles since Volkswagen AG admitted in 2015 to installing secret software on 580,000 U.S. vehicles that allowed them to emit up to 40 times legally allowable emissions while meeting standards when tested by regulators.