Turkey's President Recep Tayyip Erdogan, center, carries a coffin as he joins hundreds of mourners who attend the funeral prayers for nine members of Alemdar family killed in an apartment building collapse in Istanbul, Feb 9, 2019. (PRESIDENTIAL PRESS SERVICE VIA AP, POOL)

ISTANBUL — Turkey's interior minister says the death toll from a collapsed apartment building in Istanbul has risen to 21.

In this area, we have faced a very serious problem with illegal businesses like this done to make more money. 

Recep Tayyip Erdogan, President, Turkey

Minister Suleyman Soylu spoke late Saturday, saying those who made "mistakes" would be held accountable. 

The eight-storied building in the city's Kartal district collapsed on Wednesday.

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Rescue workers remain at the site and it is unclear how many more people are missing. The collapsed building had 14 apartments, 43 registered residents and three businesses.

Thirteen people pulled from the rubble have been hospitalized and seven remain in intensive care. Chief Doctor Recep Demirhan says that two are in very serious condition, according to Turkey's official Anadolu news agency.

Officials have said the top two floors of the building were built illegally using low quality construction materials.

Also on Saturday, President Recep Tayyip Erdogan visited the scene of the apartment building collapse for the first time, saying there were "many lessons to learn".

Turkey's President Recep Tayyip Erdogan and other officials join hundreds of mourners who attend the funeral prayers for members of Alemdar family killed in an apartment building collapse in Istanbul, Feb 9, 2019. (EMRAH GUREL / AP)

“In this area, we have faced a very serious problem with illegal businesses like this done to make more money," Erdogan told reporters at the scene.

He said the government would take "steps in a determined way" after investigators complete their work.