An on-duty New York state trooper died at an upstate lake Sunday, authorities said. 

The unidentified trooper was working a marine detail at the Great Sacandaga Lake in the foothills of the Adirondack Mountains at the time of his death, according to a statement from the New York State Police. 

It was unknown where on the 29-mile-long lake the trooper died. 

Authorities did not immediately reveal the trooper’s cause of death, which is still being investigated.