Police investigations at the scene of a fatal bin lorry crash in Glasgow are due to resume at first light.
Six people were killed when the lorry ran, apparently out of control, through city streets, on Monday.
The vehicle, operated by the city council, eventually crashed into the Millennium Hotel beside the entrance to Queen Street station on George Square.
First Minister Nicola Sturgeon said flags will fly at half-mast on government buildings out of respect.
City council leader Gordon Matheson described the crash as a "terrible tragedy".
"Our thoughts and prayers are with all those affected," he said.Police appeal
By Monday evening, eight people were being treated in hospital for injuries sustained in the crash.
The Christmas lights have also been switched off in George Square.
Police Scotland asked for anyone with photographs, videos or any type of mobile footage of the incident to contact them, using a dedicated email address.
The first casualty is believed to have been a pedestrian struck by the bin lorry close to the Gallery of Modern Art (Goma) several hundred yards from where it eventually came to rest.
The lorry flattened street signs as it travelled along Queen Street and the side of George Square.
A spokesman for the Institute of Traffic Accident Investigators said that vehicles, even large ones, can carry on for a considerable distance if there is an "unintended acceleration", which could be caused by a driver falling ill.
"Without speculating on this incident, there might be a number of causes for a vehicle to travel a considerable distance," he said.
"If there is no external influence on the steering direction of the vehicle, then it will continue in a straight line."'Simply devastating'
The Church of Scotland is inviting people to pray for those affected by the tragedy.
Minister Alastair Duncan will be leading the prayers at nearby St George's Tron Church from 11:30 on Tuesday.
The church will be open from 10:00 until 16:00 "for those who wish to say a prayer in their own time and sign a book of condolence".
Church of Scotland Moderator John Chalmers, said: "The news from the city centre of Glasgow just a few days before Christmas is simply devastating.
"For the second year in a row, Glaswegians will have to dig deep into their reserves of compassion and sympathy as they support the families of those who have been killed and injured today.
"I am sure that in these circumstances the churches and faith communities of Glasgow will do all that they can to bring support and comfort to those caught up in this tragedy and that all round Scotland and beyond; Glasgow will be remembered in the prayers of the people."
Archbishop Philip Tartaglia will say mass for the victims at St Andrew's Cathedral in Glasgow on Wednesday.