Are you following this story from Russia? The Russians lied about it numerous time, and I don’t think we can expect them to ever tell the truth. But it appears to have been a test of a highly improbably weapon (a nuclear powered missile) that resulted in either an explosion that shoved a lot of radioactive material into the atmosphere, or an actual but accidental nuclear explosion.

A village was ordered to be evacuated. Then they cancelled the evacuation.

There is evidence that the bodies of the slain scientists, and/or others injured at the site, who were blasted in the explosion, were so radioactive that the doctors that attended to them also need to be treated. It also may be the case that the nuclear device is in the sea and needs to be recovered.

This is a real mess.