German Environment Minister Barbara Hendricks submitted an official request to the Belgian government asking it to temporarily take two nuclear reactors — Tihange 2 and Doel 3— offline until they can be checked for safety, reports said Wednesday. The request comes as Berlin has voiced concerns over the two reactors several times because they are located close to the German border.

The request was made after a report from Germany's independent Reactor Safety Commission (RSK) concluded that despite the security reserves at the two reactors being sufficient for normal operations, a problem could be created in case of a fault. Belgium has two nuclear plants – one at Doel, which lies near the port of Antwerp and the other at Tihange, which lies near Leige, according to BBC. Both the plants have a total of seven reactors that help to produce 60 percent of the country energy needs.

Doel 3 was taken offline for 21 months after micro-cracks were discovered in the reactor’s pressure vessels. The reactor was shut down again on 31 Dec. 2015 after being restarted for just a few days, due to a water leak that was found, BBC reported. On Dec. 27, 2015, a fire started in the electrical supply of the Tihange plant while micro cracks were also found in the reactor.

By the end of 2015, Belgian officials had declared that the reactors were safe enough to be put back online, but Germany was concerned over the move, Deutsche Welle reported. Earlier this month, a working group from both countries met to discuss the issue.

Hendricks said in her statement, according to BBC, “On the one hand [the report] says there are no concrete indications that the reactor pressure vessels will not resist the strain; but on the other hand they say you cannot, according to today's knowledge, be sure that they'll resist every possible strain. And that's why we need further investigation.”

The BBC report added that Dutch politicians have also expressed concerns over the safety of the Doel plant, the oldest reactor of which was briefly taken offline last week.