<span style="color: #222222;">The death toll in a residential building collapse in Kartal district of Istanbul has risen to 21. </span><br />'' <br />'' <span style="color: #222222;">Till now, 14 injured people have been pulled out from the rubble. It is not yet clear how many people are still trapped in the debris of the building. </span><br />'' <br />'' <span style="color: #222222;">Officials said, prosecutors have opened an investigation into the incident. They added that illegal buildup of the top three floors of the building could be a possible reason behind the collapse.</span><br />'' <br />'' <span style="color: #222222;">Minister of Environment and Urban Planning said, a great amount of sea sand has been found in the concrete that was used for the construction of the collapsed building.</span><br />