Just did a little internet research and it appears that DNA tests were done in 2003, they were deemed inconclusive, soon controversy erupted over the validity of the testing, and it is now quagmired.
As they have undergone full conversion to Judaism, there is no reason to worry about DNA.
Typical DNA tests trace the father's lineage only. Testing the female side is more complex and less conclusive.
Jewishness requires a Jewish mother (not just Jewish descent) or a conversion process.
http://news.bbc.co.uk/1/hi/world/south_asia/4400957.stm
In the 1970s, when the Bible was translated into the local language, similarities with the customs and practices of Israeli people were noticed, Bnei Menashe members say.
A researcher of the Mizo tribe, Zaithanchuungi, developed the lost-tribe claims in 1981 and presented papers to various seminars in Israel.
Some Israeli groups like the Amishav, now known as Shavei, which helps Jews move to Israel, supported the claim and says it has brought 800 people from the Bnei Menashe to Israel.
Other Israeli groups have dismissed the claim as "historically untenable." DNA studies at the Central Forensic Institute in Calcutta suggest that while the masculine side of the tribes bears no links to Israel, the feminine side suggests a genetic profile with Middle Eastern people that may have arisen through inter-marriage.