Elite anti-terror personnel are among German investigators helping in the search for missing European tourists in Algeria.
Some fundamentalists operate in the region
Interior Minister Otto Schily said after a brief trip to Algiers that members of the GSG9 unit would not be involved in any operation to find the tourists but were there to "offer their advice in certain areas".
GSG9 are often used in hostage crises, most notably foiling the attempted hijack of a Lufthansa plane by the leftist militant Red Army Faction in the Somali capital Mogadishu in 1977.
Twenty-nine tourists, at least 15 of them German, have disappeared in the Sahara desert in the last few months.
Helicopters have been searching a huge area stretching from Ouargla in the north to the towns of Tamanrasset and Djanet in the far south of Algeria.
They use heat-seeking devices - capable of locating bodies and machines buried under sand.
Eight Austrian tourists were the latest group to be reported missing last week, when they failed to board a ferry in Tunisia as scheduled.
The German criminal investigation agency (BKA) and the Austrian Foreign Ministry have also sent officials to Algeria to work with local authorities.
Germany and Austria have issued travel warnings for Algeria, urging all their citizens to leave the country or contact their embassies.
The AFP news agency quoted a tourism professional in the region as saying that the Global Positioning by Satellite (GPS) system - which the tourists would have relied on - had not been working in the area for at least a week.
However, this would not explain the disappearance of some tourists in February.
Smugglers and drug traffickers are known to be active in the area
around southern Algeria, near the borders with Niger and
Libya, and there are fears the tourists may have been kidnapped.
The region has been relatively free of fundamentalist violence common to other parts of Algeria, but one group is known to operate there.
It is led by Mokhtar Belmokhtar, who is believed to have joined the Salafist Group for Preaching and Combat (GSPC) - a hardline organisation with alleged links to al-Qaeda.
However, authorities have said that the travellers could also have experienced vehicle problems because of sand and extreme temperatures.
Tourists have been found dead in the Sahara desert in the past, usually stranded after their fuel has run out.