HAMBURG/LONDON - Shipping on the river Danube was blocked in south Germany on Wednesday after a cargo vessel ran aground because of low water levels, a police spokesman said. Efforts are being made to remove cargo from the Romanian vessel which ran aground near Niederalteich in Bavaria, a spokesman for the Bavarian police said. It was unclear when work on the vessel would be finished it but could last until Thursday, he said. Shipping on the Danube and Rhine in Germany has been disrupted by low water this week after recent dryness in river catchment areas. The Danube is an important transport route for petroleum products and also for east European grain exports to west Europe. Around 30 inland waterways vessels are currently held up because of the blocked Danube, the police spokesman said. It was unclear whether the Danube would be immediately reopened to shipping as low water on the Isar, an adjoining river, has resulted in faster currents washing gravel into the Danube which is also hindering shipping and is currently being cleared by a dredger, the spokesman said.