Traffic was stopped in both directions on the A419 during a police-led incident near Swindon.
The major road was closed at around noon, between the B4040 and the A4311 at Blunsdon, while emergency services worked at the scene.
National Highways confirmed the closure was due to a police-led incident.
Wiltshire Police were initially unable to confirm the reason for traffic being held when approached for comment by the Adver.
They have since confirmed the road closure was due to a suspected ongoing mental health incident.
Police were called in support of ambulance crews and put a rolling roadblock in place while emergency services worked.
The road remained shut for around an hour, reopening shortly before 1pm, and traffic was at a standstill during that time.
Long queues caused some delays, but traffic dispersed quickly after being released.
A spokesperson for National Highways said: “All lanes are now open in both directions on the A419 between the A4311 and the B4040 near Swindon following a police led incident.
“Delays clearing well. Thank you for your patience.”
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