Waterbury police responded to the scene near 342 Wolcott Street at approximately 4:12 a.m. after the driver lost control of his vehicle and struck a fence and a stone wall, authorities said.
The impact left the vehicle mangled and the driver, who was alone in the car, with life-threatening injuries, according to Waterbury police.
The Naugatuck man was rushed to a nearby hospital, where his condition remains critical. Police did not release his name.
The Waterbury Police Department's Crash Reconstruction Unit is working to determine what caused the crash.
Police are asking anyone with information on the crash to contact Waterbury investigators at 203-346-3975.
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