In a separate incident late on Tuesday, three people died on the same street where the building collapsed, when a minibus became engulfed in flames, TASS news agency reported citing the local government office.
Video footage purporting to show the incident, posted on social media sites, shows a burning vehicle and some bangs are heard. A police spokesman declined to comment when contacted by phone.
The reason behind the collapse of the apartment block is still being investigated, the Investigative Committee, which probes into major cries, said on its website.
It said no trace of explosives materials had been found so far on the site. The initial reports put a possible gas leak behind the collapse.
There have been several similar incidents in the country in recent years due to ageing infrastructure and poor safety regulations about gas usage.