Boxers Rock and Tiger Allen remained hospitalized Thursday after sustaining serious injuries in a one-car accident Tuesday night in Montgomery Township.

The 29-year-old twins, who were once the city's most promising young fighters, were taken to different hospitals after being removed from a 1996 Ford Explorer that had been driven by Tiger Allen.

According to reports, the vehicle was on Bethlehem Pike when it went off the road and struck a tree. The brothers were transported from the accident scene by helicopter.

The extent of their injuries has not been released.

A call to Montgomery Township Deputy Chief Scott Bendig Thursday was not returned. An investigation of the accident is ongoing.

Rock Allen was under care at the Hospital of the University of Pennsylvania, where a spokesperson on Thursday said that he was in "serious condition."

Tiger Allen was in the intensive care unit at Hahnemann University Hospital on Wednesday. An update on his condition was unavailable Thursday.

The sons of Naazim Richardson, who is the chief trainer for Bernard Hopkins, the WBC and The Ring light heavyweight champion, Rock and Tiger Allen had been mostly inactive in the ring in recent years.

They were U.S. Olympic boxing team hopefuls leading up to the 2000 Olympics. But both were disqualified from the trials after Tiger failed to make weight at 125 pounds and was then accused of trying to weigh in for Rock in the 132-pound class. That knocked Rock out of the competition.

Rock Allen came back to make the U.S. boxing team at 141 pounds for the 2004 Athens Olympics but was defeated in the second round after receiving a first-round bye.

Rock Allen, who left the amateur ranks in 2005, hasn't fought since 2009 and is 15-0 as a welterweight. Tiger Allen turned pro in 2006 as a junior middleweight and went 3-0. His last fight was as a cruiserweight in '08.