LONDON (AP) — EDF Energy says it has shut down four nuclear reactors in England while engineers study the possibility of a technical issue in boiler units.

The units will be taken off line are in Hartlepool, in northeastern England, and in Heysham in the northwest. The move came after a fault was discovered in a boiler unit during a routine inspection.

Though EDF said Monday the problems are not considered a threat to public safety, the company notified markets of the issue because taking the reactors offline will cost EDF money and result in a hit on profits.

The company had original planned a maximum output of 63.9 billion kilowatt hours, but now plans a maximum of 61 billion.

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