Athletic director Jeff Long announced the decision and said he had no timeline in determining Petrino's future with the Razorbacks.
"I'm at the beginning of the review. I don't know what I'm going to find," Long said.
Long said he was disappointed that he didn't hear about the passenger — former Arkansas volleyball player and current Razorback Foundation fundraiser Jessica Dorrell — until a police report was released Thursday.
Petrino, who is married with four children, didn't mention he had a passenger during a news conference on Tuesday, two days after Sunday's accident, and a school statement that day quoted Petrino's family as saying "no other individuals" were involved. In a video posted by KFSM-TV, Petrino was asked following that news conference if he had another passenger with him.
"Hey coach, you said you were alone on the bike, right?" the reporter asked.
"Yeah," Petrino said before continuing to walk away.
Petrino said then that he had spent Sunday with his wife, Becky, at a lake and was going for an evening ride.
"When I came out of the ditch, there was a lady there that had flagged down a car," Petrino said Tuesday, nursing four broken ribs and wearing a neck brace to support a cracked neck vertebra. "The guy that was in the passenger's seat said, 'Get in, we'll just take you right to the hospital instead of waiting,' and so I got in the car and they headed toward Fayetteville."
In Thursday's statement, Petrino admitted that he had kept quiet about Dorrell.
"My concern was to protect my family and a previous inappropriate relationship from becoming public," he said. "In hindsight, I showed a serious mistake in judgment when I chose not to be more specific about those details. Today, I've acknowledged this previous inappropriate relationship with my family and those within the athletic department administration."
He added: "I will fully cooperate with the university throughout this process and my hope is to repair my relationships with my family, my athletic director, the Razorback Nation and remain the head coach of the Razorbacks."
Dorrell, who did not return a call seeking comment, was hired March 28 by Petrino as the student-athlete development coordinator. She is in charge of organizing the recruiting process for the football team, including initial eligibility for each incoming player.
Long said he had not decided whether to suspend Dorrell.
The police report said Petrino was riding with Dorrell when he lost control of his motorcycle. Dorrell said in the report that she wasn't sure what caused the accident, during which Petrino was unable to maneuver a turn and laid the motorcycle down on its left side while sliding off a rural, two-lane highway about 20 miles southeast of Fayetteville.
Petrino said in the report that wind and sun caused the accident. The police report said Petrino and Dorrell were taken by a passer-by from the scene of the accident to a shopping center in southeast Fayetteville, where a state police officer took Petrino to the hospital.
The police report said Dorrell wasn't taken to a hospital, and that she was dropped off at her vehicle at the shopping center.
State police spokesman Bill Sadler said Petrino didn't try to hide Dorrell's part in the accident when questioned on Tuesday.
"Coach Petrino was as cooperative as anybody that we could ever hope to encounter following the traffic crash," Sadler said. "He was very forthcoming with information when approached by the trooper who made the initial contact Tuesday afternoon."
Petrino, who wasn't wearing a helmet, was hospitalized, but has since returned to practice. He will not be cited for the accident that occurred near the small town of Crosses on a road popular with motorcyclists. Petrino has said he has been an avid rider since he was 10, and the Helena, Mont., native said several years ago that he owned a Harley-Davidson and four other motorcycles.
Petrino signed a new seven-year contract in December 2010, after completing his third regular season at Arkansas.
The contract, which was for an average of $3.53 million annually, had a clause in it that would allow Arkansas to dismiss Petrino for "engaging in conduct, as solely determined by the university, which is clearly contrary to the character and responsibilities of a person occupying the position of head football coach or which negatively or adversely affects the reputation of the (university's) athletics programs in any way."
Petrino just completed his fourth season with the Razorbacks, who have developed into a national contender under his watch. He's 34-17 in four seasons at the school, 21-5 over the last two, and the Hogs finished last season ranked No. 5 after losing only to national champion Alabama and runner-up LSU.
Petrino is a former NFL coach, leaving the Atlanta Falcons after 13 games in the 2007 season to join the Razorbacks. He endured plenty of criticism on his way out of Atlanta, from fans and former players alike, for leaving midseason.
He was a college head coach at Louisville before that, guiding the Cardinals to a 41-9 record from 2003-07.
TEXAS CHRISTIAN: Three more players have been charged with felony marijuana delivery after a six-month sting.
Defensive tackle D.J. Yendrey, linebacker Tanner Brock and offensive tackle Ty Horn are among 14 people charged on Thursday in the drug investigation, bringing the total number charged to 23. All three are charged with delivering a quarter-ounce to five pounds of marijuana.
Cornerback Devin Johnson was charged in March with three cases of delivering a quarter-ounce to five pounds of marijuana.
AUBURN: Coach Gene Chizik says linebacker Jawara White has sustained a career-ending injury.
Chizik announced Thursday that White won’t be able to play football anymore. He didn’t elaborate on the nature of the injury or whether it occurred during a practice this spring.