The death toll in a building collapse in Tehran has risen to 11 people, Iran's ISNA news agency said on Tuesday, a day after the capital's fire department said three bodies had been pulled out of the rubble.

Three people involved in the construction of the seven-storey residential building, which collapsed on Monday morning have been detained, the Resalat newspaper reported.

Officials were not immediately available for comment on the reports.

Tehran prosecutor-general Saeed Mortazavi said on Monday that around 20 construction workers were in the building when it collapsed, suggesting the death toll could rise.

He said the owners had been told to tear the building down after it started to collapse about a month ago and that the workers had been trying to salvage window frames and equipment.

A Reuters witness said the building had collapsed into a heap of rubble. Rescue workers were trying to shift the debris while sniffer dogs searched for victims and survivors.

Tehran, a sprawling city of 12 million people, has seen a boom in construction in recent years, with builders rushing to keep up with demand in the world's fourth-largest oil producer.