The Government has given an assurance it is doing all it can to find a buyer for one of the country's biggest oil refineries after it fell into administration, prompting fears of job losses and fuel shortages.
Coryton refinery in Essex, which supplies 20% of fuel in London and the South East, has halted sales and told its staff it was unsure when supplies would start again.
The refinery was operating as usual on Tuesday but no deliveries of petrol or other products, including bitumen, were leaving the site. Petrol deliveries to garages and supplies of bitumen for road building and repairs will be affected "pretty soon", unions believe.
The AA said recent disruption at refineries had been short-lived, adding its main worry was the possible effect on fuel prices. Professional services firm PwC confirmed it had been appointed as administrator to the UK arm of Petroplus, which includes the Coryton refinery, an oil storage site in Teesside and a Swansea research and development site.
The shutdown at the former BP-owned refinery - with a capacity of 175,000 barrels of crude oil per day - came as Zurich-based Petroplus said talks with its lenders had broken down and it had appointed a receiver to the UK refinery.
Linda McCulloch, national officer at the Unite union, said: "One thousand jobs are at risk but we firmly believe that joint action by the owners and Government can help secure the business."
There are seven other refineries in the UK - at South Killingholme and Lindsey, both in north Lincolnshire; Fawley, near Southampton; Grangemouth, near Falkirk; Stanlow in Cheshire; and Milford Haven and Pembroke, both in Pembrokeshire.
A Department of Energy and Climate Change spokesman said: "The refinery remains operational. We understand that a process is under way to put in place the necessary commercial arrangements to deliver product into the market.
"Companies have already made alternative arrangements to ensure adequate supply of products are available while these commercial arrangements are being put in place."
Unite said energy minister Charles Hendry assured the union that the Government was "exploring all avenues" to find a buyer for the business.