From Twitter (Pancakes included):
McClain_on_NFL John McClain Texans are going to sign Jeff Garcia as their third QB. They want 2 veterans behind rookie T.J. Yates. Jake Delhomme signed last week.
MarkBermanFox26 Mark Berman Texans have released QB Kellen Clemens and placed punter Brett Hartmann on IR.
Those are the only sources so far.
Additional info from Pancakes:McClain_on_NFL John McClain Texans worked out Jeff Garcia in each of the last 2 weeks. He used to play for QB coach Greg Knapp in San Francisco.
If Garcia failed the first two tryouts, then Clemens must be horrid.
UPDATE: Looks like some confirmation coming in:
HoustonTexans Houston Texans The #Texans have placed P Brett Hartmann (left knee) on injured reserve and released QB Kellen Clemens