The Associated Press

NASCAR driver Jimmy Spencer could face assault charges after allegedly attacking fellow competitor Kurt Busch following Sunday's GFS Marketplace 400.

As the drivers came onto pit lane at Michigan International Speedway following the checkered flag, Spencer drove into the rear of Busch's car and spun it around. Witnesses said Spencer then got out of his car, raced up to Busch's car and punched Busch several times in the face. Sheriff's deputies pulled Spencer away and took him to the NASCAR hauler.

The witnesses said Busch, who finished 18th, was holding a bloody towel to his face when he entered the track medical facility.

Jeff Patterson, spokesman for the Lenawee County Sheriff's Dept., confirmed to The Associated Press that his department was investigating an assault charge against Spencer, who finished 26th.

Both drivers left the track without comment.

This is the latest episode in a feud that was sparked when Busch bumped past Spencer in March 2002 at Bristol Motor Speedway to get his first Winston Cup victory. There have been several on-course incidents since.

"NASCAR spoke with both drivers. If we should take any actions, we'll announce it at an appropriate time," NASCAR spokesman Mike Zizzo said.

Jack Roush, who owns Busch's car, said, "Kurt says that his car ran out of gas and stopped running ... Jimmy then ran into him and came up and punched him through the window. There were words exchanged. We're going to let the authorities handle it."

Robby Gordon, another Winston Cup driver, offered to pay Spencer's fine and said Busch "had it coming for a while."

Meanwhile, Ryan Newman grabbed his series-leading fifth victory of the year, stretching his final tank of gas 52 laps on the 2-mile oval. Busch came up a lap short and wound up 18th.

"I heard (Busch) was going to be pushing his luck more than we were," Newman said. "We were close. It will be interesting to see what's left (in the gas tank)."

Newman, last year's top rookie, was 3.2 seconds behind when he moved into second, but quickly began to reel in Busch, moving up to the rear bumper of the leader's No. 97 Ford on lap 197 and charging past the slowing Busch on lap 198 after a short side-by-side battle.

Tony Stewart, the reigning series champion, finished third, followed by rookie Greg Biffle.

Series leader Matt Kenseth, who also ran the last 52 laps without stopping, wound up ninth after running back in the pack most of the day. Second-place Dale Earnhardt Jr. finished 32nd to fall 329 points behind Kenseth with 13 races remaining.