SPRINGFIELD — Baystate Health on Monday reported an outbreak of coronavirus infections at Baystate Medical Center affecting 23 employees and 13 patients.

Dr. Mark Keroack, president and CEO of Baystate Health, said the outbreak last week appears to be related in part to an employee returning to work after visiting another state identified as a “hot spot” for COVID-19.

In addition, the hospital’s “extensive review” also traced the outbreak to employees who gathered in break rooms and had removed their masks, Keroack said.

The outbreak is “deeply disappointing,” Keroack said.

“This event reinforces that COVID-19 is highly contagious and requires vigilance in order to contain its spread,” Keroack said. “We remain committed to high quality safe care and environments, and to transparency with all in our community who count on us each and every day.”

Baystate Health is not revealing the specific hospital area where the outbreak occurred, but it was not a COVID-19 unit, a spokesman said.

Patients treated in the affected hospital unit July 15-23 are being contacted so they can be tested for COVID-19 and take part in contact tracing, Keroack said.

All employees working in that area of the hospital are being tested for the coronavirus, as well as any employees who entered that area for more than 15 minutes, Keroack said.

Prior to the new outbreak, there were no documented transmissions of the virus between patients and employees, Keroack said.

“Our culture of safety is our number one priority,” Keroack said.

The hospital system has communicated with its staff to reinforce the requirements for COVID-19 safety, including frequent hand hygiene, wearing of masks and social distancing, as well as not coming to work when sick.

Baystate Health is also assessing all break areas and making alterations as needed, Keroack said.

A new policy, in alignment with Massachusetts travel restrictions taking effect Aug. 1, will require quarantine for any Baystate employee returning from a COVID-19 hot spot, Keroack said.

The hospital system already has a ban on corporate travel and meetings.

From the beginning of the coronavirus pandemic in March, Baystate Health has cared for more than 1,000 COVID-19 patients at its four hospitals, Keroack said. The hospitals are in Springfield, Westfield, Palmer and Greenfield.

Baystate Health has approximately 12,000 employees, including about 6,000 employees at Baystate Medical Center. The system has not released numbers of employees known to have contracted the virus during the pandemic.

As of Monday, there were 16 COVID-19 patients at Baystate Medical Center, including three patients in intensive care. The number of hospitalizations was also in the teens a week ago, with 13 hospitalized July 20.

“The virus will remain a real threat for many more months, and we must stay focused on taking appropriate precautions to prevent future instances of its reintroduction and spread,” Keroack said.