BOSTON (CBS) — Gov. Charlie Baker said some cases of coronavirus in Massachusetts have been traced back to large gatherings. At a press conference Friday, the governor said if this continued, it may impact the state’s ability to reopen and force stronger limits on private groups.

“We’ve seen troubling clusters developed, primarily as a result of – not so much the reopening of the Commonwealth’s economy – but related to issues associated with private recreational behavior,” said Baker. “These gatherings were planned by both adults and young people and demonstrate an, at times, unwillingness to accept the fact that this virus is extremely contagious and in many cases invisible.”

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The governor referenced specific occasions including a large lifeguard party in Falmouth, a house party in Chatham, an unauthorized football camp in South Weymouth, a high school graduation party held in Chelmsford,  a large house party in Wrentham. A 90-person prom party in Cohasset is being investigated also as a possible cluster. Lax breakroom behavior where employees took their masks off and were not socially distancing at Baystate Medical Center has caused dozens of cases, Baker said. A private party on a Bay State Cruise ship also under investigation.

The town of Cohasset said it has not seen any identified cases from the prom party, which several parents attended, but is urging everyone at the party to get tested before the town’s high school graduation Friday, Aug. 7. Several photos of the party showed people were not social distancing or wearing masks.

“While we have successfully re-opened local restaurants and shops in recent weeks, there is still a risk of exposure to COVID-19 and we must all remain vigilant in our fight against this disease,” Cohasset Town Manager Christopher Senior said.

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“People need to do their part to protect their families, their friends, their neighbors, and their communities. If you’re having an event outside, or inside and can social distance, wear a face covering.”

Baker also recommended not sharing food and drinks, and “[using] common sense.”

Current state guidance limits indoor gatherings to no more than 25 people.

“If we continue to see rises in positive test rates, we’re going to have to make some changes,” the governor said, including reducing the number of people allowed to gather.

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“Clusters from private parties are still clusters,” Baker said. “The best way to deal with a cluster is to not have one in the first place. Businesses are open, the weather is good, go outside, enjoy yourself, and do the things you know you have to do to slow the spread. Honestly, it’s really as simple as that. We want to be able to continue to be able to safely open the Commonwealth. So far, our employer community and their employees have been incredibly good about following the rules and the guidance, but we will not be able to continue to reopen Massachusetts if people can’t maintain the same discipline that they bring to work in their private activities.”