Police on Friday accused the main contractor of the concert by the popular boy band MIRROR of making false declarations about the weights of mechanical devices used.

Officers also said they arrested five people in connection with the incident during the show at the Hong Kong Coliseum on July 28 during which two dancers were injured when a giant video screen fell onto the stage.

One of them, Mo Li, who was seriously hurt, remains in hospital following treatment for his spinal injury.

Officers said four men and one woman aged between 40 and 63 were taken into custody.

The suspects include four senior staff members of the main contractor Engineering Impact who have been accused of fraud and allowing objects to fall from height.

Another suspect, from subcontractor Hip Hing Loong Stage Engineering Company, was arrested on suspicion of allowing objects to fall from height.

Speaking in a press briefing, superintendent Alan Chung of the Kowloon West regional crime unit said some of the mechanical devices used at the concert, such as LED monitors and speakers, were found to be heavier than what had been reported by the main contractor.

Police said, for example, that the weight of the speakers was seven times heavier than what had been declared.

"They made the false declarations deliberately with the view to speed up the approval process for the show," Chung said.

Officers also said there was evidence that the subcontractor had failed to follow up on operational issues during rehearsals on the day of the incident.

"From the CCTV of the Hong Kong Coliseum, we find that some staff of Hip Hing Loong, the subcontractor, have adjusted the LED panel. After that, we do not find any evidence that the company has arranged any authorised person or engineer to inspect or check the LED panel," said chief inspector Eddie Chow.

Police did not rule out making further arrests as their criminal investigation continues.