A tornado tore through a village near Stamford yesterday, throwing people into the air and ripping trees from the ground.
As it swept across Baston, eyewitnesses saw a mobile building at the nearby quarry thrown 60ft in the air before it crashed back down on its side.
It is believed six archaeology students were inside were inside. Four are believed to have been hurt, but the extent of their injuries was not clear when the Mercury went to press last night.
Five ambulances were on the scene within minutes and the air ambulance was also scrambled.
Tony Sharples, who operates the weighbridge at aggregates firm Cemex in Baston quarry, alerted the emergency services after receiving a call on his radio.
"From what I heard, a mobile building was thrown into the air and blown about 50ft to 60ft from where it had been standing. There were some archaeologists in there who had been carrying out soil tests at the site."
This mobile building and toilet were lifted off the ground
The twister struck at 2.30pm after a heavy thunderstorm. After striking the quarry it headed south-west and hit the premises of Hilton Transport.
John Falkner, 49, of Queens Road, Bourne said: "We were sitting in the office sheltering from the rain when everything suddenly went deadly quiet. We then became aware of a whistling sound and the wind just suddenly whipped up into a frenzy. We waited in the office as the thing passed directly past the premises."
John and his colleagues rushed out of the office into the yard to watch the twister move out over the fen.
He said: "We saw the funnel disappear through the back of our yard picking up gravel and peas as it hit the farmer's field – it was awesome to see so much power up close.
"We then turned round to inspect the damage and found it had a pulled trees up, one of which has fallen across five cars, writing off at least one and causing a lot of damage to the others.
Trees were ripped up and left lying across cars
"Tiles have been pulled off the roof and lots of stuff has been smashed up. It's going to take a long time to sort it all out but I suppose we are lucky to escape with or lives."
Denham Hughes, 39, of Deer Park Road, Baston, was working outside near his home when it struck.
"I noticed the clouds beginning to behave every oddly," he said. "They suddenly became very, very black and then a funnel appeared from the base. It was very long, and slender and must have been 1,000ft high.
"I jumped in my car and followed it and the damage was clear to see. It must have been very powerful because there was debris and wooden and metal sheets all over the place. It then headed towards Baston Fen, its top half disappeared, then re-formed and dissipated."
Mr Hughes, chairman of Langtoft Parish Council, said he had seen last year's tornado which hit the Deepings and that this was very different.
He said: "It was amazing. I wasn't scared because I was always a mile away but it was awesome and totally different to last year's tornado. It was very, very impressive."
Other people in Baston reported seeing and hearing debris flying round in the air, and big pieces of metal landing in their gardens.
Sibson flying instructor James Bryan, 35, was forced to land in a field.
Mr Bryan, who was flying a Tiger Moth, said: "We were informed that a weather front was moving in and were advised to land, so I landed in a field as a precautionary measure. Afterwards we were told the government radar station site had issued a red warning because of the extremely heavy rainfall, the highest on the scale."
RAF Harriers from Wittering and Cottesmore were grounded because of the poor flying conditions.
The storm also caused lights to flicker.
Met Office spokesman John Hammond said tornadoes were not an unusual occurrence during thunderstorms, but rarely caused damage on this scale.
He said: "We get about 30 reports of tornadoes every year and they are spectacular to look at, but they normally only affect small, localised areas so you rarely hear of serious damage. You don't hear of them having this kind of impact very often."
He estimated the wind speeds in the tornado could have been between 60 and 90mph.
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