Investigations are underway after a hoax bomb warning was found aboard a Turkish Airlines (THY) jet that arrived in Istanbul from the Estonian capital, Tallinn.

Turkey's national flag carrier announced on Thursday that flight TK 1422 landed at Istanbul's Atatürk International Airport at 7:15 p.m. on Wednesday. After passengers had left the aircraft, cleaners found a note written in English that claimed there was a bomb on the plane. Turkish police and bomb-disposal experts searched the whole aircraft before declaring it to be a false alarm.

One passenger, an 18-year-old foreign national, was taken to the airport's police station for questioning.

The false alarm comes three days after a THY flight attendant was detained in connection with a recent bomb scare on an international flight. The flight attendant has been accused of leaving a note warning of a bomb aboard a THY flight. Turkish Airlines confirmed Monday that the unidentified employee had been sacked after being held by police.

Wednesday's incident is the latest in a series of hoax bomb threats issued against the airline's operations that have resulted in the emergency landing of at least four international flights since the end of March.