A lorry carrying 16 tonnes of straw caught fire in a dramatic blaze next to an M3 service station on Wednesday evening (April 30).
More than 20 firefighters battled the fire, near Fleet Services, which began just after 5pm.
Diesel from the heavy goods vehicle spilled onto the road but did not ignite.
Five crews battled for several hours to bring the fire under control and were still dampening down the charred remains just after 8pm.
Motorists faced lengthy delays on the M3 with congestion stretching back to Farnborough.
Ben Ralph was driving home to Basingstoke from Milton Keynes when he witnessed the fire.
He said: "It was quite big, apparently a hay truck caught on fire on the other side of the fuel station.
"It looked like a big fire, which had been going on for over an hour. Smoke was billowing right into the motorway, slowing traffic.
"The whole area was cordoned off and there were about five fire engines present. They re-routed traffic along a service road which runs along the M3.
We were stuck in traffic for a long time."
There was no access to Fleet services and the nearby slip road was closed after the incident.
A Hampshire Fire Service spokeswoman said: "We were called at 5.13pm to the exit slip road of Fleet Services on the southbound M3 carriageway.
"A large goods vehicle which had 16 tonnes of straw was well alight. Its diesel tank had ruptured but it did not go up in flames and just spilled onto the road.
"We sent an engine from Hartley Wintney, two from Rushmoor and two water carriers from Camberley and Basingstoke.
"We are still on the scene [8.30pm] dampening down but it remains ongoing. We have been using a hose reel, compressed air foam jets and breathing apparatus."