In a statement, Ernst Russ said: “We extend our deepest sympathy to the family of the missing crew member, mindful that the search has been called off.
“Our first thoughts must be with them at this uncertain and distressing time. All necessary support is being provided to the family.”
Latest updates on the North Sea collision
The company said its focus “remains the wellbeing of our 13 crew members that were evacuated from the container ship” and added: “We also recognise the dangers that others are faced with as they work to stabilise and secure the vessels and cargos involved.”
Addressing concerns the ship was carrying highly toxic chemicals, the company said: “We are able to confirm that there are no containers on board laden with sodium cyanide… There are four empty containers that have previously contained the hazardous chemical and these containers will continue to be monitored.”
In its statement, HM Coastguard said: “The Solong is still alight and the fire on board the Stena Immaculate has greatly diminished. Safety vessels and other vessels with firefighting capabilities are still on scene with more arriving today.
“At 11.20pm last night the Solong separated from the Stena Immaculate and began to drift southwards. This is being monitored by HM Coastguard. An exclusion zone of 1km radius has been put in place around both vessels.”
The coastguard added that Defra was monitoring the situation, and air quality at ground level was currently within normal levels for the weather conditions.
The UK Health Security Agency said any public health risk on shore was deemed to be very low.
Earlier, Martijn Schuttevaer, a spokesperson for Boskalis, appointed to salvage the tanker, said the two vessels had separated overnight, which would make the salvage operation “less complicated”.
He added: “We are hoping, later today, we get close enough to the vessel to take temperature readings to determine if the fire is out.”