A Ryanair flight bound for Germany was forced into an emergency landing in Greece on Friday after a cabin window dislodged in midair. According to Greek public broadcaster ERT and other witnesses, a passenger was partially pulled through the opening before fellow travelers pulled him back inside — an account Ryanair has not itself confirmed.

Ryanair Flight FR1879 departed Thessaloniki, Greece, at roughly 6:12 a.m. local time bound for Memmingen, Germany, when the window dislodged several minutes into the flight. Flight-tracking data cited by WRAL and Simple Flying put the aircraft at approximately 16,000 feet when it turned back toward Thessaloniki, though other outlets tracking the flight reported the window failure occurred as the jet was still climbing through roughly 15,000 feet. The aircraft descended to about 6,000 feet before landing safely back in Thessaloniki roughly an hour later.

Ryanair, in a statement, said the flight “returned to Thessaloniki shortly after take-off when a passenger window dislodged inflight,” adding that the aircraft landed normally and passengers returned to the terminal.

A woman aboard the flight told ERT she heard a noise like a tire bursting before the cabin decompressed and passengers began screaming, and that “the head and shoulders of one passenger were outside the window,” according to an account relayed by Agence France-Presse.

The injured man, reported to be a Serbian citizen in his 60s, was treated for shock and other injuries after the plane returned to Thessaloniki. Ryanair said one passenger received medical assistance on the ground and that a replacement aircraft was arranged to carry the remaining travelers on to Memmingen, which it said departed Thessaloniki roughly four hours behind schedule.

Boeing said in a statement that it is “aware of the incident involving flight FR1879 and are in contact with Ryanair.”

An investigation into the incident has been launched by the Hellenic Air and Rail Safety Investigation Authority, Greece’s aviation oversight body, according to a statement from Fraport Greece, which operates Thessaloniki’s airport. Fraport said it had activated the established emergency response procedures following the aircraft’s forced return and was cooperating with investigators.

The same aircraft had also turned back to Thessaloniki shortly after takeoff on a flight to Sarajevo, Bosnia and Herzegovina, the previous evening, though the reason for that diversion was unclear.

Reporting on the incident, aviation outlet Simple Flying identified the aircraft as a Malta Air-operated Boeing 737-800 and noted that passengers seated in the row nearest the broken window were relocated before the replacement flight to Memmingen departed.