My 2 cents. The Russians took fire from an office at the first nuclear plant and returned fire. This action may have started a small blaze inside the office building which never endangered the nuclear core or power generation facility. A similar event took place at the second plant. Both sides have reason to lie. I suspect that US spy sats and or spy plane overflights can or would detect higher than normal radiation levels if there was damage to either nuclear core.
Hmmm. Fire in an office building.
Burning inconvenient documents?