One of about 1,400 contract workers involved with the refueling outage at the Limerick nuclear power plant in Montgomery County has tested positive for COVID-19, which is likely to further raise concerns of local officials who have protested Exelon Generation’s decision to proceed with the annual maintenance event.

Exelon notified county health officials that a contract worker at the Limerick Generating Station tested positive for the coronavirus on Thursday night. The worker, who is from central Pennsylvania, was last on site on Monday. The areas that the worker used have been decontaminated and plant employees were notified, the company said in a statement.

Two other full-time Limerick workers were diagnosed recently with COVID-19 at the plant, but they have not been on site since March 20, Lacy Dean, director of communications for Exelon Generation, said in a statement.

The refueling outage, which involves the influx of about 1,400 workers, began on March 27.

“The health and safety of our employees and contractors, and limiting the spread of the virus, are our utmost priorities, and we have strict protocols in place to address each case as it occurs,” the company said in a statement Friday. “Any employees who came in close contact with the affected persons or work at that reporting location are notified, and we perform an additional deep cleaning of all areas that have potentially been exposed.”

Of the 1,400 workers, Exelon said about half are local and half come from out of state. But nobody who has traveled recently overseas, or is coming in from hard-hit New York City, is permitted to work on site.

News of the infected worker is likely to heighten concern among Montgomery County officials, who have raised protests in recent days about Exelon’s decision to proceed with the refueling of one of its two Limerick reactors.

County Commissioner Val Arkoosh said at a news conference Friday that county officials have had discussions with Exelon after she expressed concern this week that the influx of workers might jeopardize the county’s efforts to combat the pandemic.

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“We are in communication with them on a daily basis, and our office of public health is working to establish a routine set of data for them to share with us every day,” she said. “They are giving us guidance on what data they are collecting.”

Arkoosh did not mention the newly diagnosed worker.

U.S. Rep. Madeleine Dean, a Democrat from Montgomery County, also expressed concern on Thursday. “While I recognize the nuclear plant as a vital part of our infrastructure, we must ensure that proper measures are taken to keep both the workers and our community safe — and limit the spread of COVID-19 as much as possible,” Dean said in a statement Thursday.

Some officials and anti-nuclear activists had suggested that Exelon should postpone the refueling event, in which a third of the nuclear fuel in Unit 1 is replaced.

“We just do not have that luxury,” Dave Marcheskie, Limerick’s communications manager, said in a video that the company posted on Thursday. Exelon officials said the refueling is required to keep the 2,260-megawatt complex operating at capacity in the summer, when its power is in peak demand.

The Department of Energy and Gov. Tom Wolf have designated power-generation plants as essential “life-sustaining” businesses that are permitted to remain open and conduct maintenance during the public health emergency. Dan Brouillette, the U.S. energy secretary, reached out on March 27 to Wolf to specifically ensure the Limerick refueling was not delayed.

Limerick is one of more than 30 reactors nationwide that are scheduled for refueling and maintenance outages this spring, according to the Nuclear Energy Institute. Nuclear operators typically schedule outages for either spring or fall, when electricity demand subsides between the heating and air-conditioning seasons, and the workhorse power plants can be taken offline without risk to the power grid.

In addition to Limerick, spring refueling outages are also scheduled or underway at operators of the Beaver Valley Power Station in Shippingport, Pa., the Susquehanna Steam Electric Station in Berwick, Pa., and the Salem Nuclear Power Plant in Lower Alloways Creek Township, N.J.

Refueling outages are planned a year in advance — tools, experts, and nuclear fuel are ordered, and work schedules are choreographed to reduce the time the plants are offline during maintenance. Nuclear power plants typically operate nearly all year, providing a constant source of electricity to the grid. Each Limerick unit powers about one million homes.

As the start date for the Limerick outage approached amid the coronavirus outbreak, the company postponed nonessential maintenance tasks it had scheduled to reduce the workforce by more than 300 people, said Lacey Dean. The outage was also extended by two days to reduce the density of workers in the plant.

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Dean said in a statement that Limerick had strict procedures in place to keep the public, employees and contractors safe, including the use of social distancing.

“As part of Limerick’s comprehensive COVID-19 safety precautions, all workers must pass a symptom screening and body temperature check prior to entry every shift,” she said. “We’re also requiring social distancing, remote work where possible, frequent hand washing, and increased facility cleaning and disinfection.”

Staff writers Allison Steele and Vinny Vella contributed to this article.