The study, carried out by a group of journalists from "Die Zeit" and "Zeit Online," looked into 222 violent attacks on refugee accommodation from over the past 12 months.

The incidents were cases in which there were injuries or the attack was of such intensity that injuries could have been caused. Since January, 104 people have been injured in attacks on refugee homes in Germany. In total, there have been 637 reported incidents.

Identifying suspects

Reporters investigating the attacks found that almost no cases had been resolved by German authorities. Only four incidents resulted in the conviction of a perpetrator, and charges were filed in another eight - which accounts for just five percent of all the attacks in 2015.

According to the study, almost all of the attacks still remain unresolved, while 11 percent of police investigations have been terminated completely. German police were able to identify a suspect in only a quarter of all cases.

Lack of police

The analysis found the reasons behind the unsuccessful police investigations to be varied. One explanation is that the crimes are often committed late at night, which enables the perpetrators to escape quickly. Many of the homes are also in quiet, suburban areas where there are few witnesses.

Another factor is solidarity within communities, which means authoritiesare often left with no lead to launch an investigation.

A lack of personnel is also having an affect on the police's ability to pursue criminals, the report said. State prosecutors have complained that there are too few arson experts, making investigations even harder.

Nationwide problem

Although the eastern state of Saxony still has the highest number of attacks, "Die Zeit" found that the problem was just as great in the West. In the western state of Baden-Württemburg, for example, authorities have been unable to solve one single aggravated attack, proving that there is still much work to be done on a national scale.