Three students living in Western University's Perth Hall have tested positive for the coronavirus with approximately 320 others on notice or part of contact tracing procedures.

The Middlesex London Health Unit declared an outbreak at the building Saturday, the second time this week students at a university residence have tested positive.

Nine students living in Saugeen-Maitland Hall tested positive Thursday and were moved into quarantine in an undisclosed location.

In a statement, the university said the three students in Perth Hall, as well as their close contacts, are also in a quarantine location.

The university also said it has "de-densified" its nine residence buildings to less than 70 per cent capacity, meaning approximately 3,589 students are housed in on-campus rooms.

"We are asking those who live in residence to limit their contacts as much as possible," said Dr. Alex Summers, Associate Medical Officer of Health with the Middlesex-London Health Unit.

In a statement, the health unit told students to avoid non-essential travel to COVID-19 hot spots, such as Toronto, which is now in the "red zone." It also said students should wear a mask outside of home, including with colleagues in breakrooms.

Eleven new COVID-19 cases were declared Saturday in the London region. Six were people in their 20s or younger.