A team of European human rights experts, who have just finished inspecting Swiss jails, say they have found no evidence of torture or abuse in the country's prisons.
But the Federal Justice Office said on Friday members of the European Committee for the Prevention of Torture (CPT) had made some recommendations for improvements in their preliminary findings.
A full report is expected in the spring of next year. It will then be sent to the Swiss authorities who will have six months to respond.
In a statement, the Justice Office said that the experts had visited prisons and other detention centres in the cantons of Aargau, Bern, Geneva, Solothurn, Valais and Zurich.
Among the institutions inspected was the Champ-Dollon prison in Geneva, which is notorious for being Switzerland's most overcrowded prison.
Justice Minister Christoph Blocher "takes very seriously" the criticisms, observation and recommendations made by the team, added the statement.
The nature of the committee's remarks has not yet been made public.
It was the fifth time that the CPT had visited Switzerland since 1991. The last visit took place four years ago when committee members conducted an "ad hoc" inspection of the secure unit at Zurich airport used for holding foreign nationals awaiting deportation.
They also examined the transit zone at Zurich airport where those refused entry to Switzerland are detained.
Although the CPT also found no evidence of torture or serious abuse at both sites, it issued several recommendations designed to improve conditions.
The main purpose of the inspection was to assess the implementation of measures adopted by the Swiss authorities after a previous CPT visit in 2001. At the time it had condemned procedures for forcibly repatriating foreigners as "inhuman and degrading".
Three years ago the Council of Europe's former commissioner for human rights, Alvaro Gil-Robles, complained about overcrowding in prisons in Geneva and Bellinzona.
Earlier this year a group of experts strongly criticised conditions at Champ-Dollon.
Plans for a national body to monitor detention centres are being delayed by Switzerland's failure to ratify the optional protocol to the United Nations Convention Against Torture.
The new global instrument foresees unannounced visits by international and national inspection teams to all detention facilities including prisons, police stations, psychiatric hospitals and asylum centres.
swissinfo with agencies
There are around 120 detention centres in Switzerland with places for 6,741 inmates.
In September last year there were 5,888 people in custody.
Foreigners accounted for 69% of the total.
Women made up 5.7%.
EUROPEAN COMMITTEE FOR THE PREVENTION OF TORTURE (CPT)
Under the European Convention for the Prevention of Torture and Inhuman or Degrading Treatment or Punishment, CPT delegations have unlimited access to places of detention.
They also have the right to unrestricted access inside secure units and can interview detainees in private.
The "periodic" visit to Switzerland is one of 11 that the CPT is undertaking in 2007. Other countries include Spain, the Netherlands, Croatia and Moldova.
After each visit, the CPT sends a confidential report containing its conclusions and recommendations to the country concerned.