Broken engine fragments smashed a cabin window of a Ryanair plane last month causing a man’s head and right shoulder to be sucked into the hole, US investigators have said.

In a preliminary report, the National Transportation Safety Board (NTSB) said this happened after an engine fan blade broke shortly after takeoff on the 10 July flight from Greece to Germany.

Serbian national Ljubisa Karović’s head and right shoulder were sucked out of the plane’s window, leaving him “seriously injured and in shock”.

His wife Svetlana Grković Maksimović later told BBC Serbia that she and two other passengers held on to his legs for several minutes.

In its report, the NTSB said the flight from Thessaloniki to Memmingen “experienced a No. 2 (right) engine fan-blade-out (FBO) failure during climb out”.

“The crew elected to return to SKG [Thessaloniki International Airport] where they made an uneventful landing.”

The NTSB was “delegated the investigation in full” by the Greek authorities in the days following the incident.

It also detailed a timeline of events given by the flight crew, who said they received a “high vibration” engine alert during the climb.

In response, they reduced the engine power and carried out a series of checks. When the vibrations stopped, the crew continued to climb on autopilot, the report said.

But the engine vibrations then increased and the crew heard a loud bang, prompting them to declare an emergency and begin their descent.

Flight attendants reported hearing and feeling the vibrations, and seeing a small amount of smoke before the oxygen masks were deployed.

One flight attendant said they then noticed passengers calling for help after a passenger became “partially lodged in a damaged cabin window”, with the entire window missing.

The engine had undergone ultrasonic inspections in May this year with no findings of fault, the report stated.

Ryanair boss Michael O’Leary earlier suggested that the incident may have been caused by “foreign object damage” to an engine.

The aircraft was operated by Ryanair’s subsidiary Malta Air.