KV Racing has been fined $5000 after Sebastien Bourdais' race-winning car from last weekend's IndyCar race at Milwaukee was found to be underweight.
The series offered no details of the infraction other than confirming that a post-race inspection determined that the car was in breach of Rule 188.8.131.52, which specifies a minimum weight of 1600 pounds for road/street courses and short ovals.
It is the third time in four seasons that a race-winning car has failed a technical inspection.
The Dale Coyne Racing car driven to victory in Houston by Carlos Huertas last year was later found to be in breach of rules dictating the fuel tank capacity and rear wing dimensions, while an illegal aero part was discovered on Justin Wilson's sidepods following his win - also with Coyne - at Texas in 2012.
IndyCar has faced criticism in the past over the relatively minor penalties imposed for irregularities with race-winning cars.
However the series' competition boss Derrick Walker told AUTOSPORT last year that a zero-tolerance approach would be unrealistic, and that the minor punishments reflected the relatively minor nature of the infractions.
Meanwhile, Chevrolet and Honda were docked 20 and 100 manufacturer points respectively for engines that failed to reach their minimum mileage at Milwaukee.
Chevrolet was penalised for the engine failure on Stefano Coletti's car, while Honda was hit with the same penalty for failures on the cars of James Jakes (Schmidt), both Coyne entries, and Wilson and Marco Andretti's Andretti Autosport entries.
Following the adjustments, Chevrolet leads Honda by 1213 points to 899.