A San Francisco-bound Boeing 777 operated by Japan Airlines was forced to return to Tokyo on Monday after its crew noticed a leak in the hydraulic system that controls the flaps, Reuters reported.

The leak was detected about three hours and 20 minutes into the more than 10-hour journey across the Pacific Ocean, and the JAL jetliner carrying 236 passengers returned to Tokyo's Haneda airport.

Maintenance engineers are investigating what caused the hydraulic system to leak, a spokesperson for the Japanese carrier told Reuters.

This incident comes just three days after an Asiana Airlines 777 crashed in San Francisco on Saturday, killing two and injuring 180 people. Although mechanical failure isn't thought to be a factor in Saturday's crash, National Transportation Safety Board chief Deborah Hersman told BBC that it is too early to speculate on the cause of the crash.

Following the crash, South Korea announced on Monday that the engines and landing equipment on all Boeing 777 planes owned by Asiana would be inspected. The government is also planning to strengthen regulations for pilots who want to shift to flying new aircraft.