"Apollo Lunar Quarantine"
Although it was indeed considered to be a remote possibility that lunar material was harmful to Earth life, a list of potential dangers was drawn up. The lunar rocks themselves could be dangerous, composed of toxic metals or chemical compounds with unknown effects on the biological systems and the physiological machinery of Earth's organisms. Although such toxicities would certainly be contained with relatively simple procedures, they would pose a risk to anyone coming into contact with the material. This was not including the indeed minuscule, but not infinitely impossible chance that life forms could survive on the Moon. It was still a possibility that these most likely microscopic life forms could either be directly harmful, or become the ultimate invasive species by thriving all too well in Earth's biosphere, replacing the native plant and animal life.
https://history.nasa.gov/afj/lrl/apollo-quarantine.html
For the "burial" scenario, see this Q&A
"And it went through our minds that, well, you might, in fact, have to sacrifice everybody in the laboratory and bulldoze it under 100 feet of dirt. "
Was emergency burial of the Lunar Receiving Laboratory planned?
Incidentally, the Lunar Receiving Laboratory building at JSC will soon be demolished.
https://www.apnews.com/19b507ff448c431182e1da1edadb4faf