A section of a bridge closed to traffic for demolition work collapsed just after noon.
Media images show rescuers working in the partially blocked underpass amidst fallen concrete slabs and a tangle of rebar.
The Hellenic Fire Service attended with 35 firefighters and three teams of emergency rescue specialists with dogs, as well as the IKAROS team with an unmanned aircraft.
The bridge had been closed by the Achaia Police Directorate since 20 July as the underpass was being reconstructed.
The Police Department of Patras is investigating and the competent prosecutor has been notified. This bridge failure comes during a state of emergency caused by wildfires throughout Greece.