The authorities seized 1,263 life jackets that failed to correspond to safety standards in the raid on the workshop in the centre of Izmir, a city on the Aegean Sea, the Dogan news agency said.
Izmir is a major hub for refugees and migrants seeking to make the risky crossing in flimsy boats to EU member Greece.
The news of the seizure comes a day after Turkish authorities announced that the bodies of 36 migrants had been found on its Aegean coast after their boats sank in bad weather while trying to cross to the Greek island of Lesbos.
Dogan said that the so-called life jackets seized were filled with "packaging" rather than the proper material needed to keep users alive for hours in the water.
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It said that four people were found working in the workshop, including two young Syrian girls. The confiscated life jackets have been sent to the local police for examination and an investigation has been launched.
AFP correspondents who reported on the wave of migrants heading from Turkey to Greece this summer had seen a booming trade in life jackets in Turkish resorts for sale at suspiciously low prices.
The International Organisation for Migration (IOM) said yesterday 1,004,356 migrants and refugees reached Europe in 2015 but 3,771 died while crossing the Mediterranean.