Scientists and healthcare workers are still trying to make sense of the many symptoms of COVID-19.

From extensive lung and blood vessel damage to the loss of smell and taste and even strange discoloration of toes, questions linger about the deadly virus currently sweeping the globe.

Now, doctors are noticing mysterious blood clots in COVID-19 patients that may be causing extremely low oxygen levels — so low that they should be unconscious or even dead — but still acting normally, according to The Washington Post.

The strange clots have even prompted some doctors have suggested giving blood thinners to all COVID patients, including the ones not sick enough to be hospitalized.

Autopsies showed that patients’ lungs were filled with hundreds of tiny clots or microclots rather than one large hemorrhage that could’ve caused a stroke or heart attack.

“The problem we are having is that while we understand that there is a clot, we don’t yet understand why there is a clot,” Lewis Kaplan, a University of Pennsylvania physician, told the Post. “We don’t know. And therefore, we are scared.”

Researchers are now investigating whether these microclots could play a role in deaths across the country.

But first, they are trying to understand what is causing them in the first place.

“One of the theories is that once the body is so engaged in a fight against an invader, the body starts consuming the clotting factors, which can result in either blood clots or bleeding,” Kaplan told the Post.