* Rights groups say heirs may be stolen Dirty War babies
* First two DNA tests come back negative, more to follow
* Battle over siblings' identity increasingly political (Refiles to fix typo in lede)
By Helen Popper
BUENOS AIRES, July 11 (Reuters) - DNA from the adopted children of one of Argentina's richest women does not match blood samples from two families who suspect the siblings were stolen as babies from political prisoners in the 1970s, legal sources said on Monday.
A 10-year battle by human rights activists to analyze DNA samples from Felipe and Marcela Noble Herrera, whose mother Ernestina owns Argentina's Grupo Clarin (CLA.BA) media empire, has become increasingly politicized in recent years.
Clarin fell out with President Cristina Fernandez after its media outlets criticized her handling of a 2008 revolt by farmers, and the president has urged the courts to clarify the identity of the Noble Herrera siblings.
State news agency Telam, citing legal sources, said the Noble Herrera's DNA did not match samples given by the Lanoscou-Miranda and the Gualdero-Garcia families.
A lawyer for Ernestina Herrera de Noble said the siblings' samples would now be compared to DNA taken from relatives of victims of the country's 1976-1983 military dictatorship and held in a genetic database.
"This shouldn't take more than 72 hours ... once the DNA has been sequenced, it's a matter of checking it on a computer," lawyer Gabriel Cavallo told local television.
"This is a positive result for us and it proves what we've been saying all along," he added.
Cavallo said the Noble Herrera siblings' decision to voluntarily submit DNA for cross-analysis last month showed they were willing to cooperate with efforts by rights group the Grandmothers of the Plaza de Mayo to find children born to women held in secret prisons during the so-called Dirty War. [ID:nN1E75N05U]
The Noble Herrera siblings, both in their mid-30s, have accused the center-left government of "harassment and persecution" and of trying to use the case to score points against their mother's companies.
Fernandez is running for re-election in October, and her campaign might be discomforted if the Noble Herreras' DNA does not match samples in the database because her government has pushed hard for them to be analyzed.
The Grandmothers group has identified 102 illegally adopted children so far, although they think there could be several hundred more who are yet to discover their true identities.
Up to 30,000 people were kidnapped and killed during the Dirty War in a state-sponsored crackdown on leftist dissent, according to human rights groups.
Many of the babies, kidnapped with their parents or born to captive mothers, were illegally adopted by military families or friends of the military junta. (Reporting by Helen Popper; Editing by Philip Barbara)