Mass production of an experimental drug given to two U.S. aid workers with Ebola may take "several months," the U.S. manufacturer said Wednesday.

International attention turned to the experimental drug known as ZMapp, developed by San Diego-based Mapp Biopharmaceutical and manufactured by Owensboro-based Kentucky BioProcessing (KBP), as Nancy Writebol and Kent Brantly, diagnosed with Ebola while treating patients in Liberia, seemed to be improving after they were treated with the medication.

"KBP is working closely with Mapp Biopharmaceutical, various government agencies, and other parties to increase production of ZMapp," KBP spokesman David Howard told Xinhua. "But this process will take several months."

Howard said in an email that the company provided "a limited amount of ZMapp" to Emory University Hospital in Atlanta, where the two are being treated, after it received a request last week from the hospital and the Samaritan's Purse, a Christian aid organization Brantly worked for.

However, the spokesman said he "cannot comment nor confirm whether ZMapp has been administered to any patient."

When asked about the company's current or targeted ZMapp production capacity, he said that information "would be proprietary."

Earlier, Mapp Biopharmaceutical said in a statement that ZMapp, a mixture of three monoclonal antibodies, was first identified as a drug candidate in January and "has not yet been evaluated for safety in humans."

"As such, very little of the drug is currently available," the company said, adding they are working to "increase production as quickly as possible." Endite