Polish police said Sunday they had arrested two men involved in stealing vans in Germany, including a vehicle which was carrying 12 bodies bound for a crematorium.
The two men, aged 25 and 27, were arrested on Thursday and Friday and are Polish nationals.
"We are sure that it is them who committed this crime, we have proof," Andrzej Borowiak, a police spokesman in Poznan in western Poland, told AFP.
In all, three vehicles were stolen on Monday night at Hoppegarten in eastern Germany. Police later found one van belonging to a building firm.
Police were searching Sunday for the other vehicles including the van that was supposed to take the bodies to a crematorium in Meissen in Saxony in eastern Germany.
Two other people are also being sought. A reward of 5,000 zlotys (1,300 euros) has been offered for information leading to the arrest.
"Everything suggests that the vehicles are on Polish soil," Borowiak said.
A Protestant pastor in Berlin has called on the thieves to return the bodies.
"Please, think how you would feel if you could not bury your mother or your father," Markus Droege said in an appeal reported by German newspapers.