A voting machine that is widely used across the country contains some parts made by companies with ties to China and Russia, researchers found, fueling questions about the security of using overseas suppliers, which has also sparked scrutiny in Washington. Voting-machine vendors could be at risk of using insecure components from such overseas suppliers, which generally are difficult to vet and monitor, said a report being released Monday by Interos Inc., an Arlington, Va.-based supply-chain monitoring company that has consulted for government agencies and Fortune 500 companies. The findings are likely to fan worries about whether voting-machine vendors are doing enough to defend themselves against foreign interference ahead of the 2020 U.S. elections, which U.S. intelligence officials say hostile powers could try to disrupt. Voting-machine vendors assailed the research, which Interos conducted independently, saying the report failed to note existing safeguards, such as testing done at the federal, state and local levels, and the vendors’ internal protocols. The report comes as U.S. lawmakers and national-security officials increasingly have sounded alarms about supply-chain risks. Although supply chains that span the globe are common in the tech industry, Russia and China pose concerns because of how, according to U.S. officials, they press companies for access to technology within their borders. Washington lawmakers have specifically cited voting machines as an area of concern, among such other products as telecom equipment made by Chinese firm Huawei and antivirus software from Russia-based Kaspersky Lab. Russia and China historically have denied interfering in U.S. politics. The report examined one voting machine as a case study. In that machine, around 20% of the components in the supply chain that Interos was able to identify came from China-based companies, including processors, software and touch screens, according to the Interos research. Those components weren’t necessarily made in China, as the suppliers may have several locations globally, and the Interos data doesn’t necessarily cover the entire supply chain, the researchers noted. Researchers declined to name the particular model of voting machine they examined, or its maker, citing the sensitivity of the issue. They said only that it is “widely used” in the U.S. Two major vendors, Election Systems & Software LLC and Dominion Voting Systems Corp., said they didn’t think it was one of their products.