Three Britons are among the dead after a Ukrainian passenger plane crashed moments after take-off from Iran, with investigators now focusing on how the plane fell out of the sky shortly after take-off.
Victims included engineer Sam Zokaei, from Surrey, Saeed Tahmasebi Khademasadi, from west London, and Mohammad Reza Kadkhoda Zadeh, from near Brighton.
All three were named on the list of 167 passengers on board flight PS752 by Ukraine International Airlines (UIA), which crashed moments after it left Imam Khomeini International Airport in Tehran at 6.10am local time (2.40am GMT) on Wednesday, bound for the Ukrainian capital Kyiv.
Nine members of crew and at least 26 children were also on board, according to the flight manifest.
Officials in Iran blamed an engine fire, while the Ukrainian president has ordered a criminal investigation into the crash.
The airline ruled out human error.
The airline said: "According to our records, the aircraft ascended as high as 2,400 metres.
"Given the crew's experience, error probability is minimal. We do not even consider such a chance."
The crash comes amid escalating tension in the Persian Gulf following the killing last week of Iranian General Qassem Soleimani by the US, prompting several airlines to reroute flights away from Tehran's airspace.
A spokesman for Imperial College London where their 35-year-old colleague – who preferred to be known as Mr Tahmasebi – was a post-graduate researcher, said: "We are deeply saddened at this tragic news.
"Saeed Tahmasebi Khademasadi was a brilliant engineer with a bright future.
"His contributions to systems engineering earned respect from everyone who dealt with him and will benefit society for years to come.
"He was a warm, humble and generous colleague and close friend to many in our community.
"Our thoughts and sincere condolences are with Saeed's family, friends and colleagues, as well as all those affected by this tragedy."
Staff at BP, Mr Zokaei's employer, also paid tribute their 42-year-old colleague.
A spokesman said: "We are shocked and deeply saddened by this tragic loss of our friend and colleague and all of our thoughts are with his family and friends."
There was no answer from the home of Mr Kadkhosa Zadeh's father in Haywards Heath.
The 40-year-old is listed as owning a dry cleaning business nearby.