"The driver was not asleep; he was well rested and had not been drinking. We cannot preempt any investigation by giving further details at this stage," a Foreign Office spokesman said.
His comments contradicted those of a minister from Tsvangirai’s Movement for Democratic Change who told AFP that the driver of the truck appeared to be sleeping when the accident happened.
The Foreign Office also said the truck which collided with Tsvangirai’s vehicle Friday, causing the death of his wife Susan and badly injuring him, was owned by a joint US-British aid project.
"We can confirm that the truck was operated by a project jointly funded by the United States and United Kingdom," a Foreign Office spokeswoman said. "All indications are that this was a genuine accident."
The Foreign Office later added said the truck belonged to a partner of the United States Agency For International Development (USAID) which delivers HIV/AIDS drugs.
The accident happened as Tsvangirai and his 50-year-old wife were travelling from Harare to Buhera, their rural hometown, for a rally.
President Robert Mugabe agreed to form a unity government earlier this year with Tsvangirai, his long-time rival, in the face of intense international pressure. (AFP)