An explosives team was on site in the town of Bovenkarspel, 55 km (35 miles) north of the capital, to examine the device, police in the province of North Holland said.
The metal remains of the explosive, about 10 cm by 10 cm (4 inches by 4 inches) in size, were found in front of the building and “must have been placed” there, police spokesman Menno Hartenberg told Reuters.
“Something like that doesn’t just happen by accident, it has to be laid,” the spokesman said.
A security guard in the testing centre alerted police to a “loud blast” that broke several windows, a police statement said.
The incident comes shortly before national elections on March 17 widely seen as a referendum on the government’s handling of the pandemic.
Anger at healthcare authorities has increased since the start of 2021, with the head of the country’s National Institute for Health now accompanied by a security detail.
Another test location was burned down during several days of rioting in January sparked by the introduction of a night-time curfew. Extra security has been provided to some locations due to threats and vandalism.
“For more than a year we have been leaning on these people on the front lines and now this. Insane,” Health Minister Hugo de Jonge said on Twitter.
The region around Bovenkarspel, a rural town, is currently suffering one of the Netherlands’ worst COVID-19 outbreaks, with 181 cases per 100,000 inhabitants, compared with around 27 per 100,000 nationally. At least one hospital has been forced to send patients to other provinces due to lack of space in its intensive care units.
Wednesday is the first day in several months when lockdown measures in the Netherlands have been slightly eased, with hairdressers reopening and non-essential stores accepting a small number of customers by appointment.
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