Things get ugly between Busch and Spencer.

The simmering feud between Winston Cup drivers Kurt Busch and Jimmy Spencer took a turn for the worse in the Michigan International Speedway garage area shortly after Sunday's GFS Marketplace 400.

Although no official report has been filed as to the exact nature of the incident it appears that Spencer punched Busch, causing possible injuries to the Roush Racing driver after some rather aggressive racing for the lead between the two shortly after the final restart of the day on lap 150.

Spencer, who drives the soon-to-be-unsponsored #7 Sirius Dodge for Jim Smith's Ultra Motorsports team, has had several on-and-off track incidents with Busch in the past, notably at Bristol and Indianapolis last year and was said to be livid with Busch's heavy-handed tactics on the track, which dropped Spencer from the lead back to third place. Making matters even worse was the fact that Busch's car then apparently ran out of fuel as everyone tried to file back into the Winston Cup garage area, causing Spencer to run into the back of him.

Spencer, Busch and their respective team owners spent more than an hour in the NASCAR trailer after the race and while Busch and Spencer both refused to comment, Busch crew chief Jimmy Fennig and team owner Jack Roush shed some light on the situation.

"What I understand is we ran out of gas on the race track and we ran out of gas here again," said Fennig, speaking in the garage area later on Sunday evening. "The car came to a stop and Spencer ran into him in the garage area. I don't know what happened after that. I wasn't around to see it."

On emerging from the NASCAR trailer, Roush added; "We had another incident and, in this case, it was after the race was over. It was in the garage. Jimmy apparently ran into, with witnesses, I did not witness it, he ran into the back of Kurt's car and that was after some contact and some exchange with Jimmy apparently being the aggressor as they went from the race track to the garage.

"Kurt says that his car ran out of gas, it stopped running. He didn't have much gas left, so Jimmy then ran into him and came up and punched him through the window. There were words exchanged. I don't know what was said. We'll get that all straight. We're gonna let the authorities handle it. The local sheriff's office is taking statements from the drivers since it was not on the racetrack and it wasn't during the event. Of course, it's primarily in Mike Helton's hands to decide what he needs to do with Jimmy after these repeated assaults that he's had, either on the race track or the rest of it.

"Jimmy has had a history of being overtly aggressive and NASCAR has taken a position on what he should and should not do about that. I haven't been part of meetings when they discussed that with Jimmy, but I know that there is some kind of a deal that they had made with him to let him continue to race unimpeded and he has broken whatever his commitment was."

Although Busch refused to talk to reporters about whether or not he was punched and sustained any injuries other than to say 'Ask Jimmy Spencer,' rumours suggest that the Roush Racing driver may have sustained a broken nose at worst and a couple of black eyes.

Spencer's punishment has not yet been dished out although, because the incident happened off the track, the local sheriffs department is currently treating it as a case of alleged assault.