BERKELEY, Calif. (AP) — A spike of coronavirus infections at the University of California, Berkeley, is tied to a series of fraternity parties, officials said.

The university had reported 23 COVID-19 cases since March but it recently confirmed 47 cases in just one week, UC Berkeley University Health Services said in a letter sent Wednesday to the campus community.

School officials said the new cases are linked to “recent parties connected to the CalGreek system.”

“These infections are directly related to social events where students have not followed basic safety measures such as physical distancing, wearing face coverings, limiting event size, and gathering outside,” they said.

The university said last month their fall semester would include limited in-person classes but the school's health officials said the recent spike in COVID-19 cases could derail those plans.