Gamma-ray emission from a narrow band at the Galactic equator has previously been detected up to 30 GeV .
We report evidence for a TeV gamma-ray signal from the Galactic plane by Milagro , a large field of view water Cherenkov detector for extensive air showers .
An excess with a significance of 4.5 standard deviations has been observed from the region of Galactic longitude l \in ( 40 ^ { \circ } , 100 ^ { \circ } ) and latitude |b| < 5 ^ { \circ } .
Under the assumption of a simple power law spectrum , with no cutoff , in the EGRET-Milagro energy range , the measured integral flux is \phi _ { \gamma } ( > 3.5 TeV ) = ( 6.4 \pm 1.4 \pm 2.1 ) \cdot 10 ^ { -11 } cm ^ { -2 } s ^ { -1 } sr ^ { -1 } .
This flux is consistent with an extrapolation of the EGRET spectrum between 1 and 30 GeV in this Galactic region .