The trail, picked up by a special cybercrime unit of the French Interior Ministry, led to a French computer specialist, Alain Quiros. He was caught in Mohammedia, Morocco, and questioned by French and Moroccan officials there (It is not clear from the case file exactly when).

Mr. Quiros initially denied any knowledge of the lab hacking, but when presented with incriminating evidence found on his computer, he confessed, telling investigators he had been paid €2,000 to €3,000, or $2,800 to $4,000, for hacking into the lab. He identified Thierry Lorho, head of Kargus Consultants, a corporate intelligence company in Paris, as having instigated the computer attack.

Then things got complicated. As the French authorities delved more deeply into Mr. Quiros’s computer, they found a copy of the hard drive of Yannick Jadot, the former campaign director of Greenpeace France, as well as that of Frédérik-Karel Canoy, a French lawyer and shareholder rights activist who has battled some of the country’s largest companies, including Vivendi and European Aeronautic Defense & Space, the parent of the aircraft manufacturer Airbus.

Mr. Lorho, a former French intelligence agent, acknowledged his role to the French officials. He told them that he had handed off the lab data to another man, Jean-François Dominguez, who had paid him for it. Both men are being formally investigated. Mr. Lorho also admitted that he had collected data on Greenpeace. His client that time, he said, was Électricité de France, which had paid him for “strategic intelligence” on anti-nuclear campaigners.

Mr. Lorho has said his contacts at E.D.F. were “perfectly aware” of the hacking and that such activities were understood to be included under the two one-year contracts he signed with the company.

One, signed in April 2004, paid Mr. Lorho’s company €12,000 a month; a second, signed in November 2006, provided for €3,900 a month.

The investigation found that in addition to information on Greenpeace in France, E.D.F. obtained data on the environmental organization’s activities in Spain, Belgium and Britain, where E.D.F. last year agreed to buy the largest nuclear power company there, British Energy.