An "unsecured" penguin in a cardboard box was the cause of a helicopter crash in South Africa, a report into the incident has found.

The penguin, which had been placed in the box and on the lap of a passenger, slid off and knocked the pilot's controls just after take-off from Bird Island off the Eastern Cape on 19 January.

The South African Civil Aviation Authority said the impact sent the helicopter crashing to the ground. No-one on board, including the penguin, was hurt.

The authority said that "the lack of secure containment for the penguin" was responsible for creating the "dangerous situation".

According to the report, released this week, the flight had been conducting an aerial survey of the island in Gqeberha, Eastern Cape province.

After completing the survey, the helicopter landed, where a specialist then requested the transport of one penguin back to Port Elizabeth.

The report did not say why they had picked up the penguin.

The aviation authority said the pilot conducted a "risk assessment" but omitted to include the transport of the penguin on board which "was not in accordance with the Civil Aviation Regulations (CAR) 2011".

When the helicopter was about 15m (50 feet) above ground, the cardboard box slid off the lap of the specialist to the right and caused the cyclic pitch control lever to move to the far-right position causing the aircraft roll, the report determined.

Unable to recover, the main rotor blades then struck the ground and the helicopter ultimately crashed on its starboard side approximately 20m from the point of lift-off.

While the helicopter sustained substantial damage, both the pilot and passengers were uninjured and the penguin was unharmed.

The report said all situations should be subject to "established safety protocols" and compliance with aviation safety procedures.

It also said that a proper evaluation of the situation and potential hazards (such as cargo shifting) should have been conducted.

"The absence of a proper, secured crate meant that the penguin's containment was not suitable for the flight conditions," it said.