Local media reports said his body was found with fractures to his legs and head at the foot of his apartment early on Monday.
Police had established that no one had entered or left his home at the time of his death, Anadolu reported.
The Istanbul governor's office said "comprehensive administrative and judicial investigations" had been initiated into Le Mesurier's death.
The private DHA news agency said authorities were investigating whether he had committed suicide, saying he had allegedly been on anti-depressant pills.
A friend of Le Mesurier, freelance journalist Oz Katerji, also reported that Le Mesurier's wife informed him that he fell from their balcony while she was asleep. His body was awaiting an autopsy.
Le Mesurier set up the Mayday Rescue emergency response group, which helped train White Helmets volunteers. "Nowhere was the impact of his important work felt so strongly as in Syria", the worldwide non-profit organisation said.
The Russian Foreign Ministry tweeted about Le Mesurier last week, alleging that he was a former agent of the UK's Secret Intelligence Service, better known as MI6.
Eddie Irvine pas très tendre avec Sebastian Vettel
En tout début d'année 2019, il avait notamment détonné en jugeant que Sebastian Vettel était "grandement surestimé" . Si vous regardez Vettel, à chaque fois qu'il est dans un duel roues contre roues, il termine derrière.
The capital goods segment, that signifies investment, contracted 20 per cent in September after a 21 per cent fall in August. The 5,2 per cent contraction in the core data for September, released on October 31, had suggested a steep drop in the IIP.
She invited others who believe they have been affected by similar circumstances to contact the department with their experiences. As well as income and creditworthiness, it also considers personal credit scores and personal debt.
Last year, I'm A Celeb ended on Sunday, December 9, so viewers can expect the show to wrap up on Sunday, December 8 this year. Ian Wright Ian Wright said he was in Australia for a golf tournament when he arrived after his jungle campmates.
"Mason Greenwood, Anthony Martial and Marcus Rashford all scored in midweek which should be good for their confidence". However, Manchester United have only managed to keep two clean sheets in the Premier League so far this season.
California Pizza Kitchen: There is a special Veterans Day menu from which veterans and military can pick one free entree. Dunkin: Vets and active duty can get a free doughnut of their choice at participating locations on Monday.
You may also have an upcoming corporate event anywhere in the US that you wish to make a permanent visual record of. As well as corporate event photography, Splento can also put you in touch with a headshot photography specialist.
Robert Kennedy, a volunteer who transported the balloon to Tuscaloosa, said the balloon began to sag as soon as it was cut. There was also plenty of bipartisan grumbling about the long lines to get in to the game due to enhanced security.
The National Weather Service Issues Winter Storm Warning
Please report snow or ice by calling 412-262-1988, posting to the NWS Pittsburgh Facebook page, or using Twitter @NWSPittsburgh. With these snowfall amounts, this will be the most widespread significant snowfall yet of the young fall/winter snow season.
Deadly NSW bushfires see state of emergency declared
Emergency services have warned of a "catastrophic threat" as raging wildfires and worsening weather conditions head for Sydney . The NSW Fire Service (NSW RFS ) has upgraded the risky fire conditions for Tuesday November 12 to include more areas.