LONDON — The police scoured the area around Salisbury, England, for a container of a deadly chemical weapon on Monday, as high-ranking British officials suggested for the first time that Russia was probably responsible for a second set of nerve agent poisonings in the region.

British officials have said that a couple who were sickened this month in the Salisbury area, one of whom died on Sunday, had been poisoned with the same powerful nerve agent used in March, a few miles away, against a former Russian spy and his daughter.

But while government officials have accused the Kremlin of responsibility for the first poisonings, until Monday they refrained from assigning blame for the second, though they acknowledged a strong possibility that the two were related.

“The simple reality is that Russia has committed an attack on British soil which has seen the death of a British citizen,” the defense minister, Gavin Williamson, said in the House of Commons. “That is something that I think the world will unite with us in actually condemning.”