Work to reopen flooded A421 'extremely challenging'
Highways bosses said it was "very difficult" to say when a severely flooded A-road would reopen.
The A421 near Marston Moretaine in Bedfordshire was closed on 22 September after a month's worth of rain fell in 48 hours.
National Highways, which maintains the dual carriageway, said it had already removed more than 24 million litres (5.3 million gallons) of water from the road, enough to fill 10 Olympic-sized swimming pools.
However, it said continued rainfall and run-off from surrounding areas was making the situation "extremely challenging".
Regional director Martin Fellows said: "Trying to put a timeline to this, when we do not yet know the condition of the road under the floodwater, is very difficult and I expect our work here will continue for the rest of this week as a minimum.
"The record rainfall this part of the country is continuing to experience is making a difficult situation extremely challenging.
"But let me reassure people our work will continue as all our effort and resources are focused on resolving this and getting the road open as soon as it is safe to do so."
National Highways said a fleet of 25 tankers and specialist high-volume pumps were working "around the clock".
It estimated about 60 million litres (13.2 million gallons) of water needed to be removed in total.
The A421 helps to connect Bedford and Milton Keynes and provides links to Cranfield University.
Parts of the region, particularly in the west, were badly affected by flooding last week, with firefighters rescuing more than 30 people from a caravan park near Oundle in Northamptonshire.
About 20 flood warnings issued by the Environment Agency remained in place.
A Met Office yellow weather warning for persistent rain was due to expire at 16:00 BST on Tuesday.
Forecasters warned of transport disruption, localised flooding and some interruption to power supplies.
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