coronavirus testing centre.Police said the blast in the Netherlands appeared to have been intentional.It went off at the facility in the town of Bovenkarspel at 6.55am on Wednesday, before it opened.Windows were shattered but no one was injured.Authorities said the site seemed to have been targeted by a metal pipe device.The metal remains of the explosive, about 4inches by 4 inches in size, were found on the front of the building.Police spokesman Menno Hartenberg said it "must have been placed" there.He said: “We don't know yet exactly what exploded, the explosives experts must first investigate."What we're saying is that something like that doesn't just happen by accident, it has to be laid.”A security guard was inside the testing centre.