A 15-year-old Australian teenager has died after he was crushed in a weightlifting accident in a gym last Tuesday (Sept 26), according to local media reports.

The teen, identified as Ben Shaw, was attempting to bench press about 100kg in a Brisbane gym when the accident happened, reported Australian news outlet ABC.

He was found pinned to the bench by a staff member of the gym.

It is not clear how long he was trapped, said ABC.

Shaw died in the hospital on Saturday.

"Ben passed away yesterday afternoon with his family and friends around him," said his family in a statement quoted by the news outlet.

"Ben was able to leave a legacy and donate his organs and tissue, giving life to others.

"We'd like to thank everyone who has been involved in Ben's care, including all friends and family."

The accident is being investigated. CCTV footage will be scutinised to determined what happened, reported ABC.

According to news reports, rules at the gym state that children under 16 years old must be supervised when using the weights equipment.

The gym's chief executive, Mr Phil Schultz, said the gym's organisation, Police Citizens Youth Club, will cooperate with the investigation.

"This is a terrible incident and everyone here at (the gym) has been impacted by it," he was quoted as saying.