A tanker carrying 2,400 tonnes of sulphuric acid has sunk on the Rhine river in Germany and police say two crew members are missing.
The tanker's other two crew were rescued, according to the authorities.
The barge capsized near St Goarshausen, south of Koblenz. Officials say they do not think any of its cargo leaked.
Thawing ice and snow have caused flooding along the Rhine in recent days but it is not known if the high river levels played a part in the incident.
German media say rescuers are using thermal imaging equipment to help find the missing crewmen.
One of the missing is Czech, the other German, according to police.
The tanker, the Waldhof, went down close to the renowned Loreley cliff near Mainz and police said the river had been closed to shipping.
"There does not appear to have been any acid leakage into the water, according to an initial, provisional investigation," Koblenz police spokesman Ralf Schomisch said.
The inland shipping authority says the tanker was heading from Ludwigshafen in southwestern Germany to Antwerp in Belgium.