The president of Mali, Amadou Toumani Toure, has said he will do all he can to find 15 European hostages believed to be held in the country.
Another group of European tourists was released in May
President Toure said he had been contacted by German officials who are convinced the hostages - 10 Germans, four Swiss and a Dutchman - are being held in the north of the West African republic.
They are believed to have been smuggled across the border from Algeria, where they were seized by armed rebels nearly five months ago.
Seventeen hostages were freed in May when Algerian special forces raided a rebel hideout.
The BBC's James Copnall, in the Malian capital Bamako, says the president's statement marks an end to the official silence about the supposed presence of the hostages in the country.
President Toure told a news conference that Mali has promised Germany it will search for the missing tourists
"Mali could not turn its back in such a situation. I do not know where they [the rebels] are hiding. The desert is big. The search is not easy," he said.
Mali and Algeria share a huge border that straddles the Sahara desert, making practical surveillance of the frontier all but impossible.
German television network ARD, said German authorities were in possession of a videotape of the hostages sending messages to their families, recorded recently in Mali.
One of the hostages, a German woman, died from heatstroke while in captivity, according to media reports.