ZBC reported that Grace was involved in a "freak" accident at the airport soon after arriving with her husband from a medical trip to Singapore.
She was treated at Trauma Centre where she was accompanied by Mugabe and was later discharged.
The state broadcaster, quoting the president's spokesperson George Charamba, did not elaborate on the nature of the accident but a source who was at the airport when it happened, said Grace's leg was dragged by the speeding car commonly known as Zim1
"The driver took off before the first lady had fully embarked," the source said. "One of her legs was still outside and she was dragged for a few metres before he stopped. I think the injuries were minor."
The source said there was no immediate explanation on what caused the mishap.
As if that was not enough, Mugabe's motorcade encountered another mysterious incident a few kilometres from the airport involving the biker.
The outrider was left for dead in the yet-to-be explained accident as they passed One Commando barracks.
According to a source who attended the scene of the accident, the outrider's elbows were heavily bruised and that suggested that he rolled several times.
Last night there were conflicting statements about his condition with some saying he was in bad shape.
Sources said the accident could have been caused by speeding as Mugabe was now rushing his wife to hospital.
"There was no evidence that the bike hit an object, nor that another car encroached onto his lane and there was no possibility that he could have hit a pole," the source said.
"It was not clear what pole or object he hit. Yes, he could have been travelling at high speed, possibly ranging between 140km and 180km per hour but the damage on the person was not relative to the damage on the bike.
"It was also not clear if the biker was alone with no other cars in the vicinity? But there was definitely no car to prove that there was encroachment. The question – what did the biker hit remained lingering?"
Charamba last night confirmed the accidents but said he did not know if the outrider was killed or not. He said the outrider could have hit a car.
"Yes, I was driving from behind and just saw that an incident had happened. I only got to know about it later," he said.
"I gather that the outrider rammed into an Isuzu but I did not check his condition because I was rushing to the hospital with the first lady."
"She was very fortunate and saved by the shoe, which slipped off her leg otherwise it could have been worse," he said.
"She went to Trauma Centre and was attended before being discharged. She only spent an hour there and she is at home now."
On Friday afternoon another biker allegedly hit a private car near State House.
Two months ago, a BMW bike outrider who was part of Mugabe's motorcade was badly injured after crashing into a Toyota Corolla vehicle while trying to clear traffic for the president's motorcade, which was on its way to State House.
In May last year; one of Mugabe's outriders also rammed into a commuter omnibus while again clearing traffic for Mugabe's motorcade. The commuter omnibus driver was charged with negligent driving.
Another Mugabe outrider died in 2012 when his bike caught fire near Sam Levy village, Borrowdale, in the capital.
During the same year, a male passenger in a minibus died after a police lead vehicle clearing traffic ahead of Mugabe's motorcade crashed into a commuter minibus carrying 22 passengers, injuring 15 other people including two police officers.
Another Mugabe outrider also hit a homeless man while the Zanu-PF leader was on his way to his Zvimba rural home the same year. The man later died.
On his return from Zvimba, an open army Land Cruiser truck carrying members of the presidential guard had a burst tyre, overturned and killed Jeoffrey Mukotekwa and injured several others.
Meanwhile, Mugabe has cancelled a trip to Mutare where he was scheduled to address over 100 000 members of the Johanne Marange Apostolic Church today, with Charamba citing jet leg.
The 93-year-old ruler was also forced to cancel a rally that was set for Lupane in Matabeleland North last Friday because he was receiving medical treatment in Singapore.
"It was a proposal (Marange trip), which I personally felt was not feasible given that he was away and affected by jet leg," Charamba said.
"I have just checked with the presidency, he is no longer going there, kindly note, this is not anyway related to the first lady incident.
"He is no longer going there because of the jet leg as you know the flight between Harare and Singapore is six hours so obviously he needs time to rest. He says he can't make it.
Mugabe spent a week in Singapore where he was making a third visit this year.
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