Uganda had been searching since Sunday morning in the Kidepo area, which is on the border with Sudan, after it lost contact with Garang’s helicopter as he returned late on Saturday from talks with Ugandan President Yoweri Museveni.
"We share the anxiety of the public since it is now 24 hours since the estimated arrival of the helicopter at its destination," said a statement issued by Museveni at around 1:30 am (2230 GMT Sunday) from his ranch at Rwakitura.
"Since (Sunday) morning, we have been searching the Kidepo area to locate the chopper without success," it said.
It added that the search was continuing and that Uganda had asked for help from Kenya, whose border is also close to Kidepo.
An accident involving Garang — who waged a two-decade war against Khartoum from southern Sudan until a peace deal in January — would be a severe blow to the country’s peace process. Under the January accord, Garang became vice-president on July 9.
The statement by Museveni was the latest in a series of conflicting reports about Garang’s fate.
Sudan’s state television carried a brief statement saying: "Reports indicate that the aircraft of the first vice-president John Garang landed safely in a camp in the south (of Sudan)."
But shortly afterwards, Sudanese Information Minister Abdel Basit Sabderat told the satellite channel Al Jazeera the aircraft was still missing.
According to the statement by Museveni: "He left Rwakitura in the President’s Mi-72 helicopter at around 1545 hours (local time) for his base at New Site (in Sudan), just north of Kidepo Valley National Park.
"Due to the need to refuel the helicopter, they stopped in Entebbe (in Uganda) and left at 1655 hours.
"By 1830 hours the chopper was overflying the Karenga and Kapedo areas near Kidepo. The helicopter attempted to land in southern Sudan at a place known as New Kush, but aborted the landing because of bad weather and headed southwest.
"It was heard over Pirre, towards the Kenyan border. Since morning, we have been searching the Kidepo area to locate the chopper without success," it said.
(Reporting by Dan Wallis in Kampala)