NEW YORK (AP) — Genzyme Corp. has shut down a key production facility as it cleans viral contamination that has been slowing down the process for making supplies of two biotech-based drugs. The biotechnology company said the virus, which is not harmful to people, was detected in one of six bioreactors at a facility in Boston, and as a precaution, it will shut down until the end of July to properly clean all of its equipment. Bioreactors are used in the production of living cells, which are in turn used to make the biotech-based drugs Cerezyme and Fabrazyme. Supplies of those drugs will be constrained because of the shutdown. Fabrazyme treats an inherited disorder known as Fabry disease, which is caused by the buildup of a particular type of fat in the body’s cells. Cerezyme treats Gaucher disease, an enzyme disorder that can result in liver and neurological problems. Genzyme said it has confirmed that the virus was the cause of two previous declines in cell productivity at the facility — located in the Boston neighborhood of Allston — and another one in Geel, Belgium. The company is adding steps to increase raw materials screening and viral removal processes. Meanwhile, Cerezyme and Fabrazyme inventories are not sufficient to meet global demand. Genzyme is still measuring the effect of the delays on Cerezyme, but the company expects temporary supply constraints to begin in September for Fabrazyme. “The patients who need these therapies are our priority,” Chairman and CEO Henri A. Termeer said in a statement. “We are confident in the quality of the products produced in Allston and in our ability to resolve the issue affecting the plant.” In a separate statement, BioMarin Pharmaceutical Inc. of Novato, Calif., said the contamination will not impact production of Aldurazyme, which treats an enzyme disorder and is marketed by Genzyme. Analysts throughout Wall Street expect the supply constraints of Fabrazyme and Cerezyme to cut into the company’s revenue during the quarter, with some estimates shaving as much as $300 million in sales. “We are unsure how quickly the facilities will be able to replace ‘lost product,’ thus we can only estimate what the value of the six-week delay is,” said Deutsche Bank-North America analyst Mark Schoenebaum, in a note to investors. He said up to $210 million in lost revenue could translate into a reduction in earnings of 18 cents per share and up to 20 cents per share with additional charges. Meanwhile, Lazard Capital Markets analyst William Tanner said a potential two-month interruption could equate to $300 million in lost sales, though the company could absorb up to $100 million of that with its current inventory. Still, the lost sales could mean a 16 cents per share cut of profit.