A Maritime Self-Defense Force panel on Tuesday released the results of a probe into an April collision of two helicopters that left eight crew members dead, with the panel’s report suggesting that insufficient coordination by commanders had played a role in the accident.

The report also singled out improper watch procedures by the crew of both SH-60K helicopters, which collided during nighttime training off a remote island near Tokyo on April 20, killing all aboard.

Defense Minister Minoru Kihara told a news conference announcing the report that his ministry had taken the results “very seriously.”