The U.S. Food and Drug Administration said on Monday it issued a warning letter to Meridian Bioscience Inc’s unit for several federal law violations after inspecting its facility that makes lead-testing devices.

The violations include selling significantly modified versions of two of its blood lead-testing systems without the FDA’s approval and failing to submit reports on the medical device after customer complained about discrepancies in the test results.

In July, the U.S. regulator issued Meridian’s unit, Magellan Diagnostics, a Form 483 for its North Billerica, Massachusetts-based facility— nearly two months after it warned that the tests may underestimate lead levels in blood.

A warning letter outlines violations in the company’s facilities, which if not resolved can lead to product seizure.

Magellan is addressing the observations noted in the Form 483 and the warning letter with the highest sense of urgency, Meridian said in a statement on Monday.

Magellan’s devices are the only lead-testing products cleared by the FDA and account for about half of all lead tests in the United States.

The company has to notify the FDA before Nov. 10 about specific steps taken to address these violations and to prevent them from recurring, the regulator said.

Meridian’s shares fell 3.8 percent to $15.20 after the bell.