An Air China flight to Beijing made an unscheduled landing in Zhengzhou city on Sunday after a passenger threatened a flight attendant with a fountain pen, the country’s civil aviation authority said, according to Reuters.

The Civil Aviation Administration said a male passenger tried to use the pen to hold the flight attendant “under duress”, but the passengers and crew were not hurt. The police said the passenger, 41, had a history of mental illness.

Earlier, the airline had said the flight had to be diverted because of “illegal interference”, Xinhua reported.

The Zhengzhou airport said it activated emergency measures as soon as the flight informed it about the incident, and that the airport was now operating normally, AP reported.

It is unclear what action will be taken against the accused passenger.