Paris ( CNN ) -- The new Human Rights Watch report `` Torture Archipelago '' documents in excruciating detail the use of torture in government detention facilities in Syria , including how , where , when and under whose command this torture was carried out . Documenting human rights violations in Syria is anything but easy , so how did we do it ? Since the beginning of anti-government demonstrations in March 2011 , Syria has been doing whatever it can to keep independent observers from finding out what exactly is going on . For many months , it refused to issue visas for such work , and widespread violations were committed with few independent witnesses . Some journalists from outside Syria bravely crossed the border without official permission , to provide valuable first-hand accounts of attacks and violations . But crossing the border illegally can be dangerous . Several journalists have been arrested and others killed on these assignments , making Syria one of the deadliest countries for journalists at the moment . News : Report describes brutal torture in Syria . In April of this year , Syria finally agreed to the deployment of 300 United Nations observers and to grant visas to some journalists , but those who got into Syria have faced difficulties on the ground . When members from the U.N. observer mission , accompanied by several journalists , tried to investigate claims of a massacre in the small village of Qubeir on June 7 , Syrian government forces initially prevented them from entering the village . When the observers finally entered the village one day later , they saw clear evidence that something terrible had happened . Journalists on the scene reported that `` the smell of burnt flesh still hung heavy in the air '' and that `` blood was in pools '' in a house . But somebody had removed the bodies . It is hard to not draw the conclusion that government forces held up the U.N. observers while somebody tried to clean up the crime scene . News : In Syria , a massacre feels eerily familiar . On June 16 , the U.N. observer mission suspended its patrols in Syria because of increased fighting . The observer mission had also come under attack on several occasions . Further complicating the work of impartial observers is the increasing amount of propaganda from both sides . We have long since stopped trusting any information coming from the government , but we can not always trust information from opposition activists either . Some are reluctant , for example , to admit that a victim was an opposition fighter , instead presenting the person as a civilian . So how does Human Rights Watch overcome these challenges ? We get the best evidence when we are able to examine the crime scenes ourselves . Despite significant risks , we have entered Syria without official permission on several occasions to investigate alleged violations . The last time , in April , we visited five towns that had just been attacked in the northern province of Idlib . We photographed bullet marks and blood traces on walls where people had been executed during the army 's attack . We interviewed neighbors who had found the bodies , and in one case , we even spoke with a wounded person who had survived an execution attempt . But rights-abusing governments can not count on hiding the truth even if they manage to keep observers out . Syrians are still leaving the country in large numbers . By comparing information from multiple , separate , detailed witness accounts , we are wresting out the truth despite the best attempts of Syria 's intelligence agencies . `` Torture Archipelago '' is based on more than 200 long and detailed interviews . We asked former inmates of government detention centers not only about the torture , but also about the layout of buildings , the location of the interrogation rooms and torture chambers , and the names of guards and fellow inmates . We documented scars and studied photographs . We asked former detainees to draw the layout of the detention floor , and we asked them to point out on satellite imagery the exact building where they were detained and tortured . We posed the same questions to defectors from the army and intelligence facilities who visited or worked in these facilities , many of whom gave us names and ranks of their superiors overseeing these detention facilities . What we found is that Syrian authorities are running a network of underground detention facilities . We have identified the locations , names of commanders , and torture methods of many of these . While the actual number is probably higher , the 27 detention facilities listed in our report are those for which multiple witnesses have indicated the same building and described in detail the torture methods being used there . By publishing this information , we are putting Syrian authorities on notice that their crimes will not stay secret . It can take time -- it has taken us several months to map these detention facilities -- but with enough perseverance , the truth will come out about the violations taking place in Syria . The question then becomes : Who will hold those responsible to account ? The opinions expressed in this commentary are solely those of Ole Solvang .
Ole Solvang : Report based on more than 200 interviews tells about Syrian government torture . Syrian authorities are running a network of underground detention facilities , he says . Solvang : With this information now public , Syrian authorities ' crimes will not stay secret . The question now , Solvang says , is : Who will hold those responsible to account ?