German police said on Friday they were conducting searches in several German towns in connection with four people believed to have ties to the suspected Vienna attacker who killed four people when he opened fire on bystanders and bars on Monday.

Germany’s BKA criminal police said on Twitter that they were searching homes and businesses in the German towns of Osnabrueck, Kassel and in the district of Pinneberg near Hamburg.

“There is no initial suspicion that the four people affected by today’s measures took part in the attack but there are believed to have been links with the suspected attacker,” they said.