(CNN) -- Researchers are putting the brakes on one of the clinical trials for a potential coronavirus treatment.
On Tuesday, the pharmaceutical giant Eli Lilly said it's pausing its ongoing trial for safety reasons.
The company did not say what happened, but the statement did say the move was recommended by independent monitors.
Clinical trials are usually paused when a volunteer gets sick or suffers a side effect.
Eli Lilly is testing what's known as a monoclonal antibodies treatment, involving immune system proteins engineered in the lab.
It's similar to the treatment made by Regeneron that was recently given to President Trump.
The announcement came a day after drugmaker Johnson & Johnson .
The company was the second vaccine maker to do that in the U.S.
The advanced trials of two other potential vaccines - made by Moderna and Pfizer - are still moving along.
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