The Times identified six operatives from Unit 29155 who appear to have been involved in the operation to kill Mr. Gebrev and the others. The three charged on Thursday arrived in Bulgaria shortly before Mr. Gebrev fell ill at a dinner with business partners in late April 2015.

Though the men were not named by prosecutors, using travel information, The Times was able to identify them by their aliases: Sergei Fedotov, Sergei Pavlov and Georgi Gorshkov. (The operatives using the names Fedotov and Pavlov were also involved in overseeing and planning the Skripal poisoning, according to European security officials.)

In Sofia, the operatives checked into a hotel near Mr. Gebrev’s offices and insisted on rooms with windows facing the entrance of an underground parking garage, investigators said. One of the men then slipped into the garage, and, according to grainy surveillance video, appears to smear a substance on the door handles of cars belonging to the victims.

That was just the first poisoning. Investigators say that after failing to kill Mr. Gebrev and the others, Mr. Fedotov and another operative returned a month later and poisoned him and his son again while they were convalescing at their home on the Black Sea. Again, they failed to kill their victims, though Mr. Gebrev says his business continues to suffer.

In the statement on Thursday, the Prosecutor General’s office said European arrest warrants and Interpol red notices — requests that other countries arrest suspects — had been filed for the three men involved in the first poisoning. It is not clear whether investigators plan to charge the other men involved in the operation.

The Kremlin is unlikely to hand over its operatives to face prosecution. After Britain announced charges against the two officers accused of involvement in the Skripal case, the men went on Russian state television to explain that they were merely sports nutritionists who had visited Salisbury to tour its famous cathedral.

Dmitri S. Peskov, a spokesman for Russia’s president, Vladimir V. Putin, did not immediately respond on Thursday to a request for comment, though in the past he has dismissed reporting on Unit 29155 as “pulp fiction.”