The organisation cites a satellite imagery of an under construction gas centrifuge facility near Mysore.
In their latest report, David Albright and Serena Kelleher-Vergantini of the Institute for Science and International Security (ISIS) said that India appeared to be finishing construction of what appears to be a second gas centrifuge facility at the Rare Materials Plant (RMP) near Mysore in Karnataka.
The report said that India is also in the early stages of building a larger unsafeguarded centrifuge complex, the Special Material Enrichment Facility (SMEF).
Noting that India's enrichment plants are not under international safeguards or committed to peaceful uses, the report said the governments and suppliers of nuclear and nuclear related dual use goods throughout the world should be vigilant to prevent efforts by Indian trading and manufacturing companies to acquire such goods for the new centrifuge complex in Karnataka as well as for the RMP.
ISIS had earlier lobbied against the India-US civic nuclear deal.
ISIS said a April 2013 high resolution commercial imagery shows that the previous year witnessed further progress at India's RMP. The building containing the suspected new enrichment facility appears externally to be nearly complete.
The report said that if it is a new facility, in addition to one that India built in 2010, the country could have more than doubled its enrichment capacity.
"Whether the plant is near operation cannot be determined from the image. The construction of other buildings appears externally complete as well, and the two storage areas seem to have developed further. Other buildings show signs of continued construction.
"The construction of two new buildings seems to be complete, while other surrounding construction continues. The construction staging area continues to be present," it said.