A building collapsed Monday in the Iranian capital, killing 19 laborers living inside it, the Iranian state television and radio said.

The collapse took place in the morning hours in the Sa'adatabad district in northern Tehran, the state TV quoted prosecutor Saeed Mortazavi as saying. The building was quickly reduced to rubble, the report said.

It added that the structure has for a month been on the verge of collapsing but the occupants refused to take municipality warnings to evacuate seriously.

The fate of another man, also a laborer living in the building, was not known. It wasn't clear if he was inside at the time of the collapse. Rescue workers were searching for survivors.

Mortazavi added that authorities promptly detained five people, including the building owner and contractors, and have warned that "serious punishment" is in store for those responsible for the "disastrous" incident.

Buildings in Tehran do not commonly collapse but old structures which the Iranian capital is known for are poorly built.