We investigated the ALMA science verification data of Orion KL and found a spectral signature of the vibrationally excited H _ { 2 } O maser line at 232.68670 GHz ( \nu _ { 2 } =1 , 5 _ { 5 , 0 } - 6 _ { 4 , 3 } ) .
This line has been detected in circumstellar envelopes of late-type stars so far but not in young stellar objects including Orion KL .
Thus , this is the first detection of the 232 GHz vibrationally excited H _ { 2 } O maser in star-forming regions .
The distribution of the 232 GHz maser is concentrated at the position of the radio Source I , which is remarkably different from other molecular lines .
The spectrum shows a double-peak structure at the peak velocities of - 2.1 and 13.3 km s ^ { -1 } .
It appears to be consistent with the 22 GHz H _ { 2 } O masers and 43 GHz SiO masers observed around Source I .
Thus , the 232 GHz H _ { 2 } O maser around Source I would be excited by the internal heating by an embedded protostar , being associated with either the root of the outflows/jets or the circumstellar disk around Source I , as traced by the 22 GHz H _ { 2 } O masers or 43 GHz SiO masers , respectively .