A Delta Air Lines flight landing in Texas requested emergency services Tuesday morning after reports of an “unknown odor or fumes” inside the cabin. When the aircraft arrived, five individuals reported falling ill.

The incident occurred in the early morning of Tuesday, Dec. 16 at the San Antonio International Airport. According to a statement shared with PEOPLE from a San Antonio Fire Department spokesperson, authorities received an initial call at 6:44 a.m. local time. The department subsequently dispatched 13 units, including four assigned to the airport.

Joe Arrington, the fire department’s public information officer, tells PEOPLE, “notes indicated an unknown odor or fumes inside the cabin” of the inbound Delta plane.

When the aircraft landed safely, all off-airport units were canceled with the exception of one EMS team.

The EMS and four airport fire department units then evaluated five individuals from the flight “who were reportedly not feeling well,” according to the statement.

Arrington tells PEOPLE none of the individuals required transport to the hospital, nor further treatment from EMS. All fire department units were finished at the scene by 8 a.m.

A spokesperson for the airport told theSan Antonio Express-Newsthat the facility received three separate medical calls on Thursday morning and confirmed one involved a Delta flight.

Delta Air Lines, the San Antonio Police Department and the San Antonio International Airport did not immediately respond to PEOPLE’s request for comment.

In a Sept. 4 post from the Federal Aviation Administration (FAA), the department stated that studies have shown aircraft cabin air is “as good or better than the air found in offices and homes.” However, rare “mechanical issues such as failures of an engine oil seal or recirculation fan bearing can cause fumes to enter the cabin.”

Plane passengers and crew members are getting sickened by toxic fumes at an alarming rateaccording to a recent analysis fromThe Wall Street Journal.

Never miss a story — sign up for PEOPLE’s free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer​​, from celebrity news to compelling human interest stories.

The outlet looked at than one million FAA and National Aeronautics and Space Administration reports, thousands of documents and than 100 interviews and found that long-term exposure to such fumes can lead to serious health issues.

Robert Kaniecki, a neurologist who’s treated dozens of pilots and over 100 flight attendants in the last 20 years for brain injuries related to fume exposure, told theWSJthe symptoms compare to a chemical concussion and the effects are “extraordinarily similar” to those experienced by NFL linebackers after taking a big hit.