ISTANBUL — Police in Istanbul have seized jewels and antiques worth an estimated $30 million from businesses in the city’s historic Grand Bazaar during an investigation into smuggled diamonds, Turkish media reported Wednesday.

The operation was launched after 10 suspects were initially detained for smuggling gems into Turkey, broadcaster CNN Turk and other outlets reported.

Acting on orders from the Istanbul Chief Public Prosecutor’s Office, police raided 23 businesses in the 15th-century covered marketplace, arresting a further 40 people.

Police confiscated some 135 pieces of jewelry, 1,132 ingots of precious metals and 267 historical artifacts with a value of 1.25 billion Turkish liras ($30.5 million), according to reports. Firearms and digital material were also seized.

The Grand Bazaar is one of the world’s most visited tourist sites and hosts thousands of small shops. It was established by Sultan Mehmet II shortly after he conquered the city from the Byzantine Empire.

Frequently described by tour guides as the world’s first shopping mall, the Grand Bazaar is no stranger to the attentions of law enforcement. In April, investigators raided a company dealing in foreign currency and precious metals over money-laundering claims.