Whalley New Road has been closed in both directions at around 1.35 today (August 26).
Police said this was due to an "ongoing police incident".
Congestion has been building along Whalley Range, Plane Street and Whalley New Road.
It is believed there has been a road traffic collision in Plane Street.
"Please be advised that Bastwell traffic lights are currently inaccessible due to an ongoing police incident," a spokesman for Lancashire Police said.
"It is currently unknown how long road closures will remain in place, apologies for any inconvenience."
More to follow...
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