Nearly 250 elementary students called in sick to St. Gregory Catholic School in Etobicoke on Monday, prompting school officials to contact Toronto Public Health and issue a school-wide warning of an outbreak of a flu virus.

In a Nov. 1 newsletter, the school’s administration told parents that a “significant number” of the school’s over 600 students were absent from school Monday morning, and many more requested to go home due to illness.

It said a number of staff members at the kindergarten to Grade 8 school were away and suffering from similar symptoms.

“Due to the high absenteeism rate, Toronto Public Health has been contacted,” the letter read.

Emmy Milne, acting manager of communications for the Toronto Catholic District School Board, said additional caretaking staff was brought in to disinfect surfaces in the school on Monday. Yesterday, fewer students were away, she said.

“As of today, the numbers have come down. There’s approximately 150 students who are away from school with flu-like symptoms,” Milne said.

Milne would not speculate on a possible connection between Monday’s outbreak and Halloween celebrations on Sunday. But she said the school’s older students participated in a dance on Friday, which may have caused the illness to spread more rapidly.