German authorities have arrested four men for throwing grenades at a home for refugees in southwest Germany, the Local reported Wednesday. Investigators said they had ruled out xenophobic violence against refugees as a motive and that the perpetrators were targeting the home's guards, who were reportedly part of a competitor's security team.

"Conflicts that exist between the security services active in the Schwarzwald-Baar district could be the cause," a police statement read. 

The men had thrown M26 grenades, made in the former Yugoslavia, over the wall of the refugee home in the January incident. While the grenades did not explode, they were live, and a bomb squad was called. Police did not reveal the names of the suspects, who were identified only as economic migrants from Eastern Europe, the Associated Press reported.

More than 1 million asylum-seekers arrived in Germany in 2015, with thousands more surging into the country in the first months of 2016. Germany has been a top destination for refugees — the vast majority of whom are fleeing violent conflict in the Middle East and North Africa — because of the country's strong economy and Chancellor Angela Merkel's outspoken welcome toward asylum-seekers.

As new arrivals wait for their asylum applications to be processed, many refugees are placed in temporary housing. Arson attacks were committed against at least 222 of those homes in 2015, and security details have been placed outside of many refugee homes and processing centers. Many of the crimes have been perpetrated in the southeast part of the country, the point of first arrival for many asylum-seekers and an area that is known for its history of neo-fascism.

"The fact that there have been no deaths yet is plain luck," Timo Reinfrank, program director at the Amadeu Antonio Foundation, which works to counter neo-Nazism, told Agence France-Presse in December 2015.