WIESBADEN, Germany — A team of international investigators said Friday that they had shut down an online marketplace for illegal drugs, weapons, stolen data and other contraband with more than one million customer accounts, illustrating how crime fighting has increasingly become a battle in cyberspace.

Investigators from the F.B.I., I.R.S. and Drug Enforcement Administration, working with counterparts in Germany and the Netherlands, spent a year and a half trying to identify and track down the people behind the site, known as Wall Street Market. It was the latest online platform to have replaced street corners and back rooms as the place to buy and sell drugs like fentanyl, stolen credit card information and fake passports.

Wall Street Market’s administrators turned out to be three young Germans, authorities said, who were arrested April 23 and 24 at their homes in German cities that are far apart from each other. The suspects, ages 22 to 31, face up to 15 years in prison if convicted. They are charged with abetting the sale of illegal drugs.

American prosecutors also charged a Brazilian man who they said had acted as a public relations representative for Wall Street Market by promoting its services on sites like Reddit, and had served as a moderator who helped resolve disputes between vendors and customers.