A door to the Kunsthal art gallery in Rotterdam, where seven valuable paintings were stolen earlier this week, had not been put on the night lock the evening the burglary took place, free newspaper Metro reports.

Security guards made the claim to the paper, suggesting the thieves might have had help from the inside.
The security guards told the paper the thieves entered the building using what is known as the ‘flipper method’, in which a hard but flexible material is placed between the door and the door post to stop locks working. This would explain why there were no signs of forced entry, the paper says.
Earlier this week, museum director Emily Ansenk said the Kunsthal’s security was ‘state of the art’ which did not require the presence of security guards overnight. She told Nos television on Friday Metro’s claim about the night lock is ‘complete rubbish’.
Overnight
Meanwhile, the AD reports that this summer, two visitors to the gallery were able to remain inside after closing time and were locked in. The room they were left in is the same one from which the seven works were stolen in the early hours of Tuesday morning.
The two visitors told the paper they eventually left through the emergency exit and it took security guards 10 minutes to notice their presence.
The seven works of art, including paintings by Picasso, Monet and Gauguin, have been valued at up to €100m.