We report a study of extended \gamma -ray emission with the Large Area Telescope ( LAT ) onboard the Fermi Gamma-ray Space Telescope , which is likely to be the second case of a \gamma -ray detection from a star-forming region ( SFR ) in our Galaxy .
The LAT source is located in the G25 region , 1 \fdg 7 \times 2 \fdg 1 around ( l,b ) = ( 25 \fdg 0 , 0 \fdg 0 ) .
The \gamma -ray emission is found to be composed of two extended sources and one point-like source .
The extended sources have a similar sizes of about 1 \fdg 4 \times 0 \fdg 6 .
An \sim 0 \fdg 4 diameter sub-region of one has a photon index of \Gamma = 1.53 \pm 0.15 ; and is spatially coincident with HESS J1837 - 069 , likely a pulsar wind nebula .
The other parts of the extended sources have a photon index of \Gamma = 2.1 \pm 0.2 without significant spectral curvature .
Given their spatial and spectral properties , they have no clear associations with sources at other wavelengths .
Their \gamma -ray properties are similar to those of the Cygnus cocoon SFR , the only firmly established \gamma -ray detection of an SFR in the Galaxy .
Indeed , we find bubble-like structures of atomic and molecular gas in G25 , which may be created by a putative OB association/cluster .
The \gamma -ray emitting regions appear confined in the bubble-like structure ; similar properties are also found in the Cygnus cocoon .
In addition , using observations with the XMM-Newton we find a candidate young massive OB association/cluster G25.18+0.26 in the G25 region .
We propose that the extended \gamma -ray emission in G25 is associated with an SFR driven by G25.18+0.26 .
Based on this scenario , we discuss possible acceleration processes in the SFR and compare them with the Cygnus cocoon .