The mangled wreckage of the open top truck lay toppled over in a canal, some 20 meters below a highway from which it apparently fell after crashing through a barrier, video and photos published by Anadolu showed.
According to DHA, the truck passengers were foreign migrants who had reached a deal with traffickers to be transported by boat to the Greek island of Samos, off the coast south of Izmir.
It was not clear where the migrants were from.
Turkey became one of the main launch points for more than a million migrants taking the sea route to EU territory in 2015, many fleeing conflict and poverty in the Middle East and Africa.
The influx of migrants was drastically curtailed by a 2016 accord between Ankara and the EU, after hundreds died crossing to Greek islands a few miles off the Turkish shore.
The truck driver lost control of the vehicle and it crashed at around 8 a.m. (0500 GMT) in the Gaziemir district, near the airport south of Izmir city, DHA said.
A CNN Turk correspondent at the scene said emergency workers had worked to retrieve the dead and wounded trapped beneath the truck.
DHA said five people, including the driver were seriously injured, while Anadolu said 11 were injured and taken by ambulances to nearby hospitals.