Thousands of people heading to London for one of the biggest weekends in the sporting calendar could be affected by the partial closure of the M1.
The motorway has been shut both ways between junctions one and four, between Brent Cross and Elstree, Hertfordshire, since Friday after a scrapyard fire.
The capital is hosting two FA Cup semi-finals and the London Marathon.
The Highways Agency said a decision on when to reopen the M1 would not be made until 1000 BST.
The fire, which involved some gas cylinders, broke out near to Scratchwood Services at 0410 BST on Friday.
London Fire Brigade said about 50 people living in properties near the scrapyard were evacuated as a precaution while the cylinders were cooled and made safe.
A Highways Agency spokeswoman said engineers had been given access to the site of the fire underneath the motorway and checks now had to be carried out on the seven-mile stretch of road to ensure it had not been damaged by the blaze.
Fans travelling to Wembley later for the FA Cup semi-final between Manchester City and Manchester United were advised to find an alternative route or means of travelling.