SAN FRANCISCO — Amid rare extreme heat in San Francisco, it was unusual to see black smoke billowing from a chimney on Friday — not to mention that it was coming from the Russian Consulate, the day after the Trump administration ordered it closed.

Neighbors gathered on the sidewalks to gawk; the Fire Department came to investigate; local environmental officials sent an inspector. This being California, there were concerns about pollution.

But a darker conspiracy theory was also in the air: that the Russians were burning documents ahead of what a Foreign Ministry spokeswoman in Moscow described as a search of the building scheduled for Saturday by American security services.

“Maybe they are shredding first and burning what they shred,” said one woman standing on the tree-lined sidewalk outside the consulate on Friday afternoon, identifying herself only by her first name, Marion. “I don’t care what they do as long as fire doesn’t start coming out the windows.”