In the letter, the USFDA said inspectors during January 27 to February 4, 2015, had found significant deviations from standard manufacturing practices at the company's Hinjwadi, Pune-based plant.
The significant violations included non-adherence to appropriate written procedures, poor sterilisation practices and unreliable environmental and personnel monitoring, the US health regulator said.
Elaborating on the violations at the plant, the USFDA said "operators crawled on the floor on their hands and knees under the filling line during routine aseptic filling operation activities".
"Your environmental monitoring (EM) and personnel monitoring (PM) data are not reliable because of the materials and procedures you use to conduct EM and PM tests," the USFDA said.
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The facility design may represent an additional contamination risk to the products it manufactures, the USFDA noted.
"Furthermore, data falsification and manipulation, and your reliance on incomplete records to release product to the market, are repeat violations," the US health regulator said.
Until all corrections have been completed and FDA has confirmed corrections of the violations and the firm's compliance with CGMP, FDA may withhold approval of any new applications or supplements, the USFDA said.
The FDA issued the letter on March 3, and has given the company 15 days to respond. The company could not be reached for comments over the FDA letter.