The 12 were arrested and held in custody at a police station in Plymouth on suspicion of causing criminal damage or conspiracy to cause criminal damage.
Their arrest followed an incident on Monday night when a security guard at the National Institute of Agricultural Botany (NIAB) at Hood Farm, Dartington, called the police saying that around 20 people in white suits were in the field spraying the crop.
The eight men and four women, aged between 20 and 40, came from the Manchester and Bristol areas. Samples of the spray used on the crops was sent for analysis.
Dr John Macleod, the NIAB director, said: "I personally find it very frustrating that people take the law into their own hands to destroy the evidence which will allow an informed decision."
First reports said the trial area which contained one genetically-modified variety of maize and four conventional control varieties was destroyed.
He said the Institute, independent of government and industry, had "no axe to grind" and its sole objective was to produce sound scientific data to enable informed discussion and eventual decision.
Monday night's attack occurred even though the NIAB had hired security guards following a raid a week ago by a different group of protesters in which several hundred square metres of conventional maize were destroyed. In this attack the protesters missed their target - the genetically modified crop. The two are indistinguishable in appearance.
A statement yesterday from a group called the Genetic Engineering Network said that 30 "concerned citizens", many from the Totnes area, had taken "direct action" aimed at preventing the pollination of a genetically engineered crop.
l House of Commons officials last night confirmed that they took the decision to try to keep genetically-modified food out of Commons bars and restaurants. The decision was taken by officials and not by MPs on the House's all-party catering committee.Reuse content