A man arrested on suspicion of killing 12 people by mowing through a Berlin Christmas market in a truck has been released, the Chief Federal Prosecutor's Office says.
"The investigation up to now did not yield any urgent suspicion against the accused," the prosecutor's office said in a statement on Tuesday.
The prosecutor's office said the suspect had made extensive statements during a police hearing, but had denied the offence.
It added it had been impossible to track the truck driver by eye-witnesses following the attack and that the investigation so far had not been able to prove that the suspect was in the truck's cab at the time of the attack.
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His release comes after police chief Holger Muench warned one or more of the perpetrators of a truck attack at a Berlin Christmas market may still be on the loose.
"We are, of course, highly alarmed and we are investigating - of course - in all directions," Muench said at a press conference in response to a journalist's question earlier on Tuesday.
Officials had admitted they were uncertain whether the now released Pakistani suspect was in fact the driver of the vehicle that ran through the market on Monday night, killing 12 people and injuring 48.
Another suspect, a Polish national who was a passenger in the truck, was found shot dead at the scene.
The Polish truck driver whose vehicle was used in the attack had arrived hours earlier in the German capital and spoken to his wife about 3pm, according to his cousin.
When she called again an hour later, there was no answer.
"The phone was just silent, silent. He should have picked up if he was on a break, particularly if his wife was calling," said the cousin, Ariel Zurawski, who was also the boss of the trucking company.
"At 3.45pm you can see the movement on the GPS. The car moved forward and back. As if someone was learning to drive it," Zurawski told Polish public broadcaster TVP Info on Tuesday. "I knew something was wrong."
At about 8pm local time, the lorry slammed into a crowd of people thronging the wooden stalls of the Christmas market next to the Kaiser Wilhelm memorial church at the heart of west Berlin.
Zurawski said he had identified his cousin Lukasz, whose last name has been withheld, from police photographs that showed him with a swollen, bloodied face.
"The police told me he had been not only stabbed but also shot," Zurawski said.
