Roger Penske has warned his NASCAR team to stay out of any controversy regarding the possible manipulation of tires used during races.

The team owner is aware of rampant industry speculation that some crews are drilling tiny holes in tires to allow air to escape during a race.

NASCAR has confiscated tires the last two weeks for further inspection. The tires from Kevin Harvick and Team Penske driver Joey Logano were taken after the race in Phoenix, but NASCAR said both teams were clean.

Four drivers had their tires taken after California last week and the results haven't been made available.

Penske believes any team caught manipulating tires should face a potential ban from NASCAR.