More than 70 Humber College students at a campus residence fell ill Thursday night with some type of gastrointestinal illness, but the cause of the sudden outbreak remains unknown.

The students all live at the one residence on the north campus at Highway 27 and Finch, and started reporting feeling ill late in the afternoon, according to Andrew Leopold, director of communications.

More students fell ill as the evening wore on, he told CBC Toronto early Friday morning.

The school's dean of students later told reporters that of the 77 students in total who got sick, 30 were taken to hospital.

"All students who were transported were treated and released and returned to residence throughout the night," Jen McMillen told reporters outside the school.

Toronto Public Health investigating

The students were all suffering from symptoms like vomiting and abdominal pain, she said. Some of the school staff members who were helping students at the residence through the night have also developed the symptoms, according to McMillen.

More than 70 Humber College students at a campus residence fell ill Thursday night with some type of gastrointestinal illness, but the cause of the sudden outbreak remains unknown. 0:24

The source of the illness has not yet been determined, she said when asked whether food poisoning may be to blame. To her knowledge, food was still being served on campus.

The school notified Toronto Public Health (TPH), McMillen said. The city agency focused on food poisoning when addressing CBC's questions on Friday.

Dr. Michael Finkelstein, associate medical officer of health, said TPH has opened an investigation, which includes speaking to officials at the hospital where students were treated, as well as health-care personnel at the school.

"TPH will be reaching out to the students who reported that they were ill today to gather more information such as where they ate and what food they ate before they became ill and if they attended any specific functions where food was served before they became ill," Finkelstein said in a statement provided to CBC.

'Nobody wants to come out of their rooms'

Students who were outside the residence Friday described the atmosphere in the building.

"Nobody wants to come out of their rooms," Duncan Lotoski told CBC.

Lotoski was in bed around 9:30 p.m. ET when he noticed flashing lights through his window. When he looked out, he saw a number of ambulances.

"Then you hear supervisors in the halls handing out masks saying, 'Wash your hands, wash your hands,'" he said. "I just stayed in my room for the rest of the night."

Jazz McClean said friends who have fallen ill are convinced they got food poisoning.

"It was wild," he said of what it was like inside the residence building overnight. "There were people on the floor."

Meanwhile, classes and other services on campus were not affected on Friday, McMillen said.

Students are being instructed to rest, drink lots of fluids and to "practice good hygiene," she said.