A 20-year-old college student — the daughter of a Port Authority cop killed on Sept. 11 — died after choking on pancakes during an eating competition at Sacred Heart University in Connecticut, officials said.

Caitlin Nelson, of Clark, New Jersey, who served as the vice president of community service at the school’s Kappa Delta sorority, was taking part in the Greek life eating contest last Thursday when she began choking after eating four or five pancakes, witnesses told police.

“She starts to choke on a pancake and someone recognized it — one of the nursing students at the competition — and she caught her and brought her slowly to the ground,” Fairfield police Lt. Robert Kalamaras told The Post. “And then she began CPR, basic life support, until officers showed up less than two minutes after the emergency call was made by one of the nursing students.”

Responding officers then tried to clear Nelson’s airway, but to no avail. She was rushed to St. Vincent’s Medical Center and was later transferred to the Columbia University Medical Center — where she died Sunday, Kalamaras said.

Nelson was a junior at the school, where she studied social work and served on the executive board of the university’s Kappa Delta sorority, according to her LinkedIn page and the organization’s website.

Messages seeking comment from university officials were not immediately returned Monday, but thousands of students attended a memorial vigil for Nelson on Sunday.

“Heaven got another angel and we are sad beyond belief for Caitlin’s family,” one user wrote on a Facebook post of the vigil. “No family should have to endure the loss of a child ever and they already lost her dad on 9/11, it’s heart wrenching.”

Nelson’s father, James, was a Port Authority police officer who died during the Sept. 11 terrorist attacks on the World Trade Center when Caitlin was just 5 years old, the Connecticut Post reports. The 40-year-old cop also helped evacuate the area after the 1993 bombing.

Last September, 15 years after the attacks, Caitlin Nelson posted a picture on Facebook of herself with her father.

The 18-year vet was survived by his wife, two daughters, brother and sister, according to the Officer Down Memorial Page.

Kalamaras said Caitlin Nelson had several food allergies, but it was later determined by doctors that they were not a contributing factor to her death. Nelson had several friends at the competition who were aware of her allergies and she had all necessary emergency information listed in her cellphone for emergency responders, who initially thought she was suffering from anaphylactic shock, Kalamaras said.

University officials said Monday that flags flew at half-staff on campus in honor of Nelson.

“Counseling services have already been provided, in particular for Caitlin’s sorority sisters, and will continue to be available for all members of the SHU community who may need them over the next few days,” communications director Deborah Noack told the Fairfield Citizen in a statement.