According to officials of Tsvangirai's political party, the Movement for Democratic Change, the head on collision with a lorry was not a genuine accident.
Rumours that the fatal incident was a botched assassination attempt spread quickly in the country, which has a history of political killings.
Tsvangirai was heading to his rural home Buhera for a rally on Saturday, Mar 7 when the crash occurred on Friday afternoon. From his hospital bed in Harare he told one of his aides that a large truck driving on the other side of the road had come toward his Land Cruiser, the middle vehicle in a three-car convoy.
The truck driver told the police that he had fallen asleep at the wheel, Murira added.
The crash, coming less than a month after Tsvangirai was sworn in as Prime Minister in a tense and long-negotiated power-sharing government with his rival, President Robert Mugabe. But most officials were careful to say that not enough was known about the collision to make any accusations of foul play.
Tsvangirai has been the victim of multiple assassination attempts during his years as an opposition leader. Last year, he fled the country, fearing for his life, after he outpolled Mugabe in March presidential elections.