(CNN) -- It's a startlingly familiar story: a violent crash during a car race sends debris hurtling into the stands. Spectators scatter, some are hurt.
It happened again Sunday at IndyCar's Grand Prix of Houston, where 13 spectators were injured when two cars bumped in the final lap of the race, sending one sailing into a protective fence while the other spun out, shearing off part of its side of sending debris toward the grandstands. One of the drivers, three-time Indianapolis 500 winner Dario Franchitti, suffered spinal and ankle injuries and was hospitalized.
The incident comes eight months after a February accident during a NASCAR race at Daytona International Speedway that spewed debris into the stands, injuring 28 fans. In March two people, a driver and a 14-year-old boy who was standing in the pit area of a California racetrack, died in an accident during warm-ups.
While it appears no one keeps comprehensive statistics, the Charlotte Observer newspaper reported in 2011 that 46 spectators had died at U.S. race tracks between 1990 and 2010. The newspaper did not track injuries.
PRESS Inc., a racing safety company, cites insurance industry sources as saying 2,000 spectators are injured in a year.
In a statement issued Monday, IndyCar said it "is thoroughly reviewing the incident. Reducing the risks that are associated with racing is one of our highest priorities and receives our constant and on-going focus."
The issue of fan safety has long been on IndyCar's agenda. The issue was amplified two years ago, when two-time Indianapolis 500 winner Dan Wheldon died after his car struck a fence support during a race in Las Vegas.
Last year, a league consultant said the league was committed to investigating ways to better design barriers to prevent crash debris from reaching fans, according to IndyCar.com.
And in May, league CEO Mark Miles said executives would look at new safety initiatives, including the possibility of new types of fences, more safety precautions near where drivers stop for service and repairs, and driver safety enhancements.
NASCAR took similar safety precautions after February's wreck at Daytona International Speedway by adding extra cables on crossover gates and tethering frames of gates to posts.
CNN's Dan Moriarity contributed to this report.