Ivana Trump, Donald Trump's first wife, died of "blunt impact injuries" to the torso, the New York City medical examiner's office has said.
It added that the death of the 73-year-old on Thursday was accidental.
Reports in US media say she died after falling down stairs in her New York City apartment.
Ivana Trump, who was born in what was then Czechoslovakia, married the former president in 1977. They divorced 15 years later in 1992.
"She was a wonderful, beautiful, and amazing woman, who led a great and inspirational life," Mr Trump said.
They had three children together - Donald Jr, Ivanka and Eric Trump.
Donald and Ivana Trump were notable public figures in New York in the 1980s and 1990s, and their split was the subject of intense public interest.
After their separation, Trump went on to launch her own lines of beauty products, clothing and jewellery.
She took credit for bringing up their children in her 2017 memoir Raising Trump, saying she "made the decisions about their education, activities, travel, child care, and allowances" until college.
In the book, she added that her relationship with Mr Trump had improved since their divorce, and said she spoke to him about once a week.
The Trump family lauded her in a statement as "a force in business, a world-class athlete, a radiant beauty, and caring mother and friend".
"Ivana Trump was a survivor. She fled from communism and embraced this country," the statement added. "She taught her children about grit and toughness, compassion and determination."
Ivanka Trump, who was said to be very close to her mother, said in an Instagram post she was "heartbroken".
"Mom was brilliant, charming, passionate and wickedly funny. She modelled strength, tenacity and determination in her every action. She lived life to the fullest - never forgoing an opportunity to laugh and dance," she wrote.
Donald Trump was Ivana's second husband. Her first, Alfred Winklmayr, was an Austrian ski instructor and friend who she reportedly married in order to obtain Austrian citizenship.
That marriage allowed her to leave Czechoslovakia, her communist home country, without defecting.
BBC
Russia's unmanned Luna-25 spacecraft has crashed into the Moon after spinning out of control, officials say.
Donald Trump has confirmed that he will not take part in Republican presidential debates with his rivals in the race for the White House.