Eighteen residents at a Tokyo hospital have tested positive for the new coronavirus after around 40 trainees ignored repeated calls not to join large gatherings and attended a dinner party, the hospital said Monday.

Keio University Hospital said one trainee doctor tested positive for the coronavirus on March 31, and subsequent tests found 17 more infections among 99 trainees who might have been in close contact with the first trainee. The infected 18 residents included those who did not attend the party, according to the hospital.

“This is an intolerable act from people engaging in medical care who should protect patients. I offer my deep apology,” Yuko Kitagawa, head of the hospital, said in a statement.

The 99 trainee doctors have been ordered to stay home for two weeks. The hospital did not disclose when the approximately 40 trainees gathered for the dinner party.

The infections come at a time when Tokyo, Osaka and five prefectures brace for a state of emergency to be declared on Tuesday over the pandemic.

People in Japan have been urged to stay home and avoid public gatherings to prevent further spread of the virus.