At least 38 people were killed when a small passenger plane crashed near the Iranian capital Tehran, state media reports.
The aircraft, which was heading to the eastern city of Tabas, went down after take-off in a residential area near Mehrabad airport on Sunday morning.
Passengers included at least five children, the aviation authority said.
Iran has suffered a series of plane crashes, blamed on its ageing aircraft and poor maintenance record.
Initial reports said all passengers on board the plane had been killed, but state media later reported that some passengers had been injured and transferred to hospital.
Iran is still flying planes bought before the Islamic Revolution in 1979. International trade sanctions were imposed after the hostage crisis which followed, during which 52 Americans were held captive in Tehran for 444 days.
The latest incident involved an Iran-140 plane said to have been carrying 48 people, including 40 passengers and eight crew.
State TV said the pilot detected technical issues four minutes after take-off and tried to return to the airport, but the twin-engine turboprop crashed on a road at 9.18 local time (4:38 GMT).
President Hassan Rouhani has expressed his condolences to the families of the victims.
He also ordered a halt to all flights of the Iran-140 pending full investigation, the state-run news agency Irna reports.
An Iranian MP has blamed the aviation authorities for the crash.
Mehrdad Bauj-Lahuti, who sits on a parliamentary committee that deals with infrastructure, said officials should not have allowed the plane to fly after it suffered malfunction during test flights.
Many Iranian planes are fitted with unofficial spare parts. There have been more than 200 accidents involving Iranian planes in the past 25 years, leading to more than 2,000 deaths.