According to the Federal Aviation Administration, the pilot reported a fire alarm cockpit.
The incident happened just before 10 a.m. Saturday.
The pilot was able to return safely to the departure point. No injuries were reported and the incident was under control by 10:15 a.m.
The emergency landing comes just a week after the airline made another emergency landing at Newark Airport.
A United Flight on the same route to Puerto Rico was forced to return to Newark after a mechanical issue was reported.
Passengers on that flight were also returned to the airport safely.
The FAA is currently investigating the cause of the fire alarm.
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