Denmark has suspended its use of AstraZeneca’s COVID-19 vaccine, while regulators examine reports of people who have been vaccinated developing dangerous blood clots.

There is no proven link between the AstraZeneca jab and those blood clots, but the Danish health authority said Thursday that it was pausing the vaccine’s distribution for two weeks as a precautionary measure.

“Right now we need all the vaccines we can get. Therefore, putting one of the vaccines on pause is not an easy decision,” said National Board of Health director Søren Brostrøm. “But, precisely because we are vaccinating so many people, we also need to respond with timely care when there is knowledge of possible serious side effects.”

Denmark, which has at least partially vaccinated nearly 10% of its population, was among 17 European countries issuing vaccines from a million-dose AstraZeneca batch labeled ABV5300. The others are Austria, Bulgaria, Cyprus, Estonia, France, Greece, Iceland, Ireland, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Poland, Spain, and Sweden.

Earlier this week, Austrian authorities suspended the distribution of doses from the batch, following the death of a 49-year-old nurse who had received one, and a pulmonary embolism from which a 35-year-old vaccinated nurse is recovering.

Estonia, Lithuania, Luxembourg, and Latvia followed suit. And now Denmark has suspended its use of all AstraZeneca doses, following a report of a death in that country.

AstraZeneca said Thursday that it was aware of the Danish decision.

“Patient safety is the highest priority for AstraZeneca,” the company said. “Regulators have clear and stringent efficacy and safety standards for the approval of any new medicine, and that includes [AstraZeneca’s COVID-19 vaccine]. The safety of the vaccine has been extensively studied in Phase III clinical trials, and peer-reviewed data confirms the vaccine is generally well tolerated.”

The Danish health authority told Fortune it was now awaiting further information from both the Danish and EU drug regulators. Danish Prime Minister Mette Frederiksen said the department’s decision to pause the rollout was “the right way to do it.”

The European Medicines Agency, which cleared AstraZeneca’s vaccine for EU-wide use at the end of January, said Wednesday that its safety committee was investigating the two Austrian cases possibly associated with batch ABV5300, plus two other reports of clotting.

“There is currently no indication that vaccination has caused these conditions, which are not listed as side effects with this vaccine,” it said. “Although a quality defect is considered unlikely at this stage, the batch quality is being investigated.”

The agency pointed out that 5 million people in the European Economic Area have received AstraZeneca’s vaccine so far, and there have been 30 reported cases of clotting. “The information available so far indicates that the number of thromboembolic events in vaccinated people is no higher than that seen in the general population,” it said.

Nonetheless, the news has hit AstraZeneca hard, with its share price falling more than 3% on the news of the Danish suspension.

Of the vaccine makers whose products have thus far been approved in the EU, AstraZeneca is the only one to sell its vaccine at cost. Its rollout has been tumultuous, however.

This is partly because of delivery shortfalls that led the EU to consider (and, in the case of Italy, apply) bans on the export of AstraZeneca doses, and partly because of regulators disagreeing about the jab’s suitability for older people.

This article was updated to include new AstraZeneca vaccination figures from the European Medicines Agency.