A vessel carrying 2,400 tonnes of sulphuric acid has capsized on the Rhine in Germany.
The accident has forced the closure of the river to shipping near Loreley in the west of the country.
But for now it appears there is no danger from the acid.
Emergency services official Ronald Eppelsheim said:
“According to what we know right now, no sulphuric acid has escaped. Two members of the crew have been saved, but two are still missing. On the left and right banks of the Rhine all fire brigades are being deployed. And we hope we can still get someone out of there.”
Authorities say the barge is believed to have a double hull, which would prevent pollution.
The vessel was sailing to the Belgian port of Antwerp.