"The players are in no mood to play the series. We are just waiting for the green signal to fly home," the source said on Wednesday.
South African team manager Gordon Templeton told AFP the tourists were awaiting word from Cricket South Africa over the independent security assessment by the International Cricket Council (ICC).
"We have not heard anything yet on the ICC report," Templeton said.
South Africa had earlier indicated they wanted to return home following a blast close to their team hotel on Monday which killed seven people and injured eight.
The Proteas, however, agreed to extend their stay in Colombo pending the security assessment by the ICC which was expected to be announced later on Wednesday.
The Indian team have decided against cancelling its tour following increased security and positive indications from the Indian diplomatic mission in Colombo.
It is understood that Sri Lanka will ask India to play a bilateral one-day series if South Africa pull out. A formal announcement of the new series will be made later.
South Africa played a two-Test series in Sri Lanka earlier on their tour without incident. The home team won both matches against the depleted tourists, missing captain Graeme Smith and all-rounder Jacques Kallis.
The tri-series, which was scheduled to start on Monday, has not seen a ball being bowled in the first two matches.
The original opener between South Africa and Sri Lanka was rained off on Monday and cancelled again on Tuesday following South Africa's reluctance to play amid security fears.
The next match between India and Sri Lanka was abandoned on Wednesday due to wet ground conditions at the Premadasa stadium.