MDC’s spokesperson Nelson Chamisa said the party’s national executive committee would investigate whether foul play was involved in the accident.
Tsvangirai’s wife, Susan, was killed when a truck crossed into the opposite lane late on Friday and slammed into their vehicle which was driven by a private, not government, driver.
She was thrown out of the car, which overturned and rolled three times, and was pronounced dead on arrival at hospital.
Tsvangirai suffered some head and neck injuries and chest pains, but his condition was stable, Chamisa and Tsvangirai’s family members confirmed.
The head of casualty at the Harare hospital where Tsvangirai was being treated, Dr Douglas Gwatidzo, said the prime minister may be released from the hospital on Saturday.
State television showed pictures of Tsvangirai in a neck brace, which Gwatidzo said was being used to keep him comfortable.
"We might release him today or tomorrow," Gwatidzo told reporters gathered at the hospital.
Ian Makone, a secretary to the prime minister and member of the MDC, said Tsvangirai was " devastated by the death of his wife".
Tsvangirai, who turns 57 on Tuesday, had six children with Susan (50), who was very popular among MDC supporters. They used to chant "mother, mother" when she appeared at rallies with her husband.
She avoided the political spotlight but stood by Tsvangirai throughout his ordeals as Mugabe’s most determined opponent.
The crash occurred on the outskirts of Harare on a decrepit road notorious for accidents. Like many in Zimbabwe, it is in poor condition because it has not been maintained.
A United States embassy official, speaking on condition of anonymity because the official spokesperson was not immediately available, said on Saturday that the truck involved was transporting medicine for Aids patients donated by the US government. It was driven by a Zimbabwean contracted by the US.
State television said the truck swerved on an uneven stretch of road. Tsvangirai’s spokesperson James Maridadi earlier said Tsvangirai’s car sideswiped the truck and rolled at least three times.
The state-run newspaper the Herald reported on Saturday that the two other people in Tsvangirai’s car — the driver and a bodyguard — were also injured. The paper added the driver and occupants of the truck were taken to a police station, but it was unclear whether they had been arrested.
Police spokesperson Superintendent Andrew Phiri told the Herald the truck may have struck an object on the road before it veered.
The couple had been headed to a weekend rally in Tsvangirai’s home region, south of Harare.
President Robert Mugabe spent about an hour at the hospital late on Friday. He and other senior aides who also visited did not speak to reporters or Tsvangirai supporters gathered outside.
Several world leaders expressed their condolences to Tsvangirai.
"We know and know too well the pain and sorrow that death has brought to bear on you personally, the family and indeed the entire Zimbabwe nation," South Africa’s President Kgalema Motlanthe said in a statement.
Britain and the US, both supporters of Tsvangirai, sent condolences.
Tsvangirai was sworn in on February 11 as Zimbabwe’s prime minister in a power-sharing deal meant to end almost a year of deadly stalemate with Mugabe. The unity government was formed under pressure from neighbouring leaders who wanted Zimbabwean leaders to turn their attention to a growing humanitarian and economic crisis after years of rivalry between Tsvangirai, a former trade union leader, and Mugabe, in power since independence from Britain in 1980.
Tsvangirai formed the MDC a decade ago.
As it emerged as a serious political challenger, Tsvangirai repeatedly faced the wrath of Mugabe’s Zanu-PF. He has been beaten and was once nearly thrown from a 10th floor window by suspected government thugs.
Zimbabwe has the world’s highest official inflation rate, a hunger crisis that has left most of its people dependent on foreign handouts and a cholera epidemic blamed on the collapse of a once-enviable health and sanitation system. — Reuters, Sapa-AP