Investing.com -- Indian authorities opened an investigation Tuesday into an Air India Airbus A320neo aircraft following a momentary altitude variation during flight, the government said.

The authorities secured the aircraft's Flight Data Recorder and Cockpit Voice Recorder for examination.

Air India flight AI2379, traveling from Phuket, Thailand, to Delhi, lost altitude suddenly during cruise. The aircraft was carrying 137 passengers and eight crew members.

The flight landed safely in Delhi at 5:37 a.m. GMT. Eight passengers and four crew members sustained injuries and were transported to hospital for medical evaluation, the government said.

Air India said it informed relevant regulators and is cooperating with the investigation. The airline also notified the aircraft manufacturer.

The aircraft is a 7-year-old Airbus, according to Flightradar24.