CAMBRIDGE, Mass. (AP) -- Biotechnology company Genzyme Corp. said Tuesday it will face production delays on two key drugs because of a manufacturing issue at its Allston, Mass., facility.

The issue will cause supply constraints for Cerezyme and Fabrazyme, which are used to treat enzyme disorders.

The company said it has to interrupt production while the plant is sanitized of a virus that was found in one of its six bioreactors. Genzyme is working with regulatory agencies as it cleans the facility. It expects the plant to be fully operational again by the end of July.

The virus strain has not been shown to cause human infection, but it interferes with cell growth, which is part of the process used to make biotech drugs.

Genzyme said it has confirmed that the virus was the cause of two previous declines in cell productivity at the Allston facility and another one in Geel, Belgium.

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 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.

Shares fell $4.13, or 7.4 percent, to $51.49 in premarket trading. The stock has ranged from $50.05 to $83.97 over the past year.