A witness saw a man being pinned to the ground and arrested by armed police after a crash in the Alwoodley area of Leeds.
Officers have been on the scene in King Lane since 10am this morning and a huge area has been cordoned off after a van flipped onto its roof.
Several police vehicles and forensic collision investigators are in the area.
A number of other vehicles appear to have been involved in the collision.
One witness who lives nearby said: "Armed police were here earlier this morning and targeted a silver Lexus.
"One man was pinned down by police and arrested."
Another witness said: "The first thing I heard was the noise of a police helicopter, then a huge bang and when I looked out there were around 20 police vehicles fifty yards from my home.”
There is still a large police presence in the area.
West Yorkshire Police have been approached for more information.
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