Police in South Africa sought to establish the origin of diamonds at the heart of Naomi Campbell's testimony at the war crimes trial of former Liberian leader Charles Taylor.
"Our enquiry needs to determine that fact and that is what we are going to be busy with," Musa Zondi, spokesman for the South African police special investigations unit, told AFP.
"Possession of uncut diamonds is an offence. Ours is to search for truth and we are investigating the offence and who might be responsible."
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Campbell testified on Thursday that she had received "dirty-looking stones" after a dinner she attended in Pretoria in September 1997 that was hosted by then president Nelson Mandela, with Taylor among the other guests.
Assuming they were from Taylor, she gave the stones to Jeremy Ratcliffe, then director of the Nelson Mandela Children's Fund, who held onto them until last week when he turned over the three small uncut diamonds to police.
Investigators have confirmed they are diamonds, but their origins remain a mystery.
Prosecutors at the Special Court for Sierra Leone want to prove that Taylor, 62, dealt in so-called blood diamonds to buy weapons for rebels who murdered, raped and maimed civilians during Sierra Leone's 1991-2001 civil war.
Taylor denies the allegations.
In a statement, Ratcliffe said he accepted the stones from Campbell because "I thought it might well be illegal for her to take uncut diamonds out of the country".
While Campbell wanted the charity to make use of the stones, Ratcliffe said he did not want to involve it in possible illegal activities, adding: "In the end I decided I should just keep them."
Hollywood star Mia Farrow, who also attended the dinner, testified on Monday that Campbell had named Taylor as the man who sent her a "huge diamond," while Campbell's former agent Carole White said there were about six rough stones.
South African police said prosecutors would have to decide whether to file any charges against Ratcliffe, who kept the diamonds in secret for 13 years.
"A factor that influenced me not to report the matter to anyone was to protect the reputation (of the children's fund), Mr Mandela himself and Naomi Campbell, none of whom were benefitting in any way," said Ratcliffe.
