Gaborone - Three luxury cars belonging to the Mugabe family were briefly detained in Botswana after the vehicles were involved in a crash as they were driven out of Zimbabwe, police said on Tuesday.The Rolls Royce Ghost, a red Porsche and a Range Rover were damaged when the convoy - led by former first lady Grace Mugabe's son - slowed down to avoid cattle crossing the road.The vehicles were hit by a Toyota Corolla near the village of Artesia, 80km northeast of the capital Gaborone, in the nighttime accident on Friday, police said."We kept the vehicles for few hours at the police station and they were released to the owners on Saturday morning," superintendent Wazha Zambezi told AFP."We always keep the vehicles involved in accidents and those three cars were not an exception."Grace Mugabe has not been seen in public since her husband Robert Mugabe was ousted from power in November after a military intervention that ended his 37-year reign.The Chronicle, a state-owned newspaper in Zimbabwe, reported this week that Grace's son Russell Goreraza had been stopped at the border for several hours as he drove into Botswana.The cars were suspected of being used to smuggle cash and other valuables out of Zimbabwe after Mugabe's fall.They were released after several hours of searches and when Goreraza produced documents proving that Grace had granted him permission to drive her Rolls Royce to Botswana and South Africa.The paper reported that Goreraza said he was driving to South Africa to have the cars serviced.Goreraza is Grace's son from her first marriage. She also has two sons and a daughter with Robert Mugabe, 93.Grace, who is 41 younger than her husband, was widely criticised for her extravagance and lavish shopping sprees as the Zimbabwean economy collapsed under Mugabe's authoritarian rule.