The A23 has been closed after a suspect package was found near a bridge at Handcross.
Some homes have been evacuated in the area and both lanes of the A23 between Pease Pottage and the A272 at Bolney have been closed.
The Horsham Road at Hancross has also been closed while police examine the package to discover if it is dangerous.
A Sussex Police spokesman warned drivers to avoid the area.
They received a call about the package at about 12noon today.
He said the roads would be re-opened when it was deemed safe.
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