Two German construction companies are taking part in rebuilding Russian-occupied Mariupol, the Ukrainian city that fell to Moscow's invading forces two years ago, a German press investigation claimed on Thursday.The industrial Knauf group, which manufactures plasterboard, and WKB Systems, which produces aerated concrete, have been providing materials for construction in the city that was almost entirely flattened during the early months of the war, according to the investigation by Monitor magazine and shown on the public ARD television channel.Monitor says it has analyzed numerous images from construction sites where the Knauf logo appears, as well as detailed activity reports demonstrating the German company's presence in the port city.Mariupol fell to Russian forces after a two-month siege that cost the lives of thousands and left the city in rubble.The magazine also quotes an "official distributor" of Knauf's that is promoting a housing project in Mariupol, built with Knauf products on behalf of the Russian Defense Ministry.Products from WKB Systems, which is majority-owned by Russian businessman Viktor Budarin, can also be seen at construction sites in Mariupol, the magazine said.Knauf, in a statement sent to AFP, insisted it "respects all the EU, U.K.
and American sanctions against Russia."The Bavarian group runs 14 production sites in Russia where it employs 4,000 people.It said its decision not to pull out of Russia as many major German groups did following the invasion was out of "responsibility" to its employees.Since conquering Mariupol, Russia has published a reconstruction plan for the city, which was home to more than 400,000 Ukrainians before the invasion."Any enterprise participating should ask itself at whose service it is putting itself," Germany's foreign ministry told AFP, describing Russia's reconstruction claim as "propaganda."Germany's economy ministry told AFP that authorities needed to determine whether or not the participation of German companies represented "a violation of sanctions."