Commerce Secretary John Bryson said Monday night that he is taking an indefinite leave of absence to deal with health problems, after officials said the Cabinet member had a seizure while driving Saturday and was involved in three traffic collisions.

Bryson’s leave was announced after 10 p.m. Monday. It followed a day of confusion about his medical condition and about the crashes that led to Bryson being cited for felony hit-and-run in California. In a memo released to reporters, Bryson said his leave would last “during the period of my illness.”

“I notified President Obama this evening that effective immediately I am taking a medical leave of absence so I can focus all of my attention on resolving the health issues that arose over the weekend,” Bryson wrote. He said his second in command, Rebecca Blank, would be the acting secretary in his absence. Blank has already served in that capacity, filling in after former secretary Gary Locke left to be ambassador to China.

Bryson did not say more about the nature of his health issues. Neither did the White House, which said that “President Obama’s thoughts are with Secretary Bryson and his family during this time.”

The length of Bryson’s leave is undetermined, and a Commerce official said late Monday that he is undergoing tests and will consult with doctors before making a final decision about whether to return to work.

Bryson, 68, is the newest permanent member of Obama’s 21-person Cabinet, taking his post in October. His leave ended a tumultuous day in which White House officials conceded that they had not learned of Bryson’s accidents until a full day after they occurred. They acknowledged that, even two days afterward, they did not fully understand what had happened.

Bryson was driving alone when his Lexus ran into two other cars shortly after 5 p.m. Pacific time Saturday — hitting one of the vehicles twice. Nobody in the other cars was seriously hurt. After the third crash, Bryson was found unconscious behind the wheel. He was treated overnight at a Los Angeles area hospital.

On Monday, Commerce Department spokeswoman Jennifer Fried­man said the secretary had suffered a seizure — his first — at some point during the incident. She said toxicology tests confirmed that neither alcohol nor drugs played a role in the crashes. A spokesman from the Los Angeles County Sheriff’s Department declined to comment on the tests.

On Monday, however, it was unclear what caused Bryson’s seizure and what part it played in the collisions. The secretary has “limited recall” of the events, Friedman said. The Los Angeles County district attorney will decide whether to prosecute him, based on the felony citation he was issued for leaving the scene of an accident.

Aides said Monday that Bryson flew back to Washington on Sunday night, but he made no public appearances. At the White House, officials seemed to be struggling to understand what had happened to Bryson.

Obama talked to local TV anchors Monday, and KTIV, the NBC affiliate in Sioux City, Iowa, asked him about Bryson. “I haven’t spoken to him,” the president said. “I just found about this today. My hope is that he’s doing all right. We’re still trying to find out. It sounds like it was health-related in some way. But we’re going to make sure, obviously, that he gets the best care and we’ll be able to make a determination from there.”

White House press secretary Jay Carney said in a news briefing Monday afternoon, “We’re still in the process of gathering information about it.”

Carney said the White House was notified of the crashes Sunday night, a day after they occurred. Bryson talked with White House Chief of Staff Jacob J. Lew on Monday.

“As the matter stands right now, is the secretary healthy and fit to serve?” a reporter asked Carney.

“I would refer you to the Commerce Department for details on Secretary Bryson and his health and more details on this incident,” Carney said.

Bryson has been in office for eight months, tasked with being the White House’s liaison to a sometimes mistrustful and occasionally hostile U.S. business community. His background suited him well for both worlds: He began his career as an environmental activist, then was an executive at a California power company.

On Thursday, Bryson was in California, where he has a residence, delivering a commencement address at the private high school from which four of his children graduated. On Saturday, police said, Bryson was driving south on a four-lane road through an industrial section of the Los Angeles suburb of San Gabriel.

He was alone, without the security detail that accompanies him on official business and in Washington. As he drove, police said, a Buick ahead of him stopped for a train. Bryson ran into the Buick, police said, then got out of the car and spoke with the three men inside. Police didn’t divulge what Bryson said, but they stated that he did not give his name and address, as California law requires after an accident.

Then Bryson left, striking the Buick again, police said.

“The three males followed him in their car while calling San Gabriel police officers via 911 and asking for assistance,” police said.

About five minutes later, Bryson was involved in another crash on a separate stretch of the same commercial road. His Lexus hit a Honda Accord with two occupants, police said.

When officers arrived, they found Bryson unconscious behind the wheel. The Commerce Department said that he was taken to a hospital for observation and that he received “medication to treat seizures.”

The two passengers in the Buick and the passenger in the Accord “complained of pain” after the crashes, but were not taken to a hospital.

If Bryson had not been hospitalized, he probably would have been arrested, said Lt. Ariel Duran, the San Gabriel police watch commander on Saturday.

Instead, police cited him for felony hit-and-run and told him to appear in Superior Court in Alhambra, Calif., in 60 days.

Studies suggest that about 8 percent of Americans will have a single seizure in their lifetimes. Often the cause is never known.

In some cases, a “partial complex seizure” can leave a person able to perform simple, familiar activities but not more complex ones. The cause is abnormal electrical discharges occurring in one part of the brain but not others.

“Patients may continue driving, just not very well,” said Gregory L. Krauss, a neurologist and epilepsy specialist at Johns Hopkins University. “They don’t have normal awareness. They might be able to turn a bit but not do complex avoidance maneuvers.”

Such seizures can last for four or five minutes. Some also become “generalized,” affecting the entire brain and leading to unconsciousness. Even if that doesn’t happen, people are generally confused for up to an hour afterward.

The Commerce Department, where Bryson occupies a large office facing the Ellipse, is a sprawling enterprise with disparate divisions ranging from the Census Bureau to the Bureau of Economic Analysis and the National Oceanic and Atmospheric Administration.

For Obama, the department has been a rare source of turnover in a generally stable Cabinet. During the 2008 transition, he first tapped then-New Mexico Gov. Bill Richardson (D) to lead the department, but Richardson withdrew his nomination just days later amid an ethics investigation.

In a bid for bipartisanship, Obama then turned to Sen. Judd Gregg (R-N.H.), who initially accepted the offer but withdrew his name in the early days of the administration, citing disagreements with the president’s economic policy . Finally, Obama tapped former Washington governor Gary Locke (D) for the position. Locke’s tenure is perhaps best remembered for his stewardship of the 2010 Census and because he was the first Chinese American to hold a Cabinet position. But he left last year to serve as U.S. ambassador to China after Jon Huntsman Jr. resigned.

The White House, responding to criticism that Cabinet members lacked private-sector experience, then considered several corporate executives to fill the position, including the Office of Management and Budget’s current acting director, Jeffrey Zients, a former D.C. area business executive.

Instead, Obama tapped Zients to lead a possible reorganization of the department and named Bryson to the job in May 2011. The Senate confirmed Bryson in October after GOP senators delayed a vote in order to secure changes in U.S. trade policy.

A former executive at Edison International, Bryson is a co-founder of the Natural Resources Defense Council and once served on the boards of Boeing and Walt Disney Co.

He has maintained a low profile in Washington, in part because the administration has rarely made him available to the media. Some officials privately say he is not the strongest public advocate for the administration’s economic and trade policies — even though they initially billed him as a high-profile liaison to the corporate world.

Staff writers David Brown and Debbi Wilgoren contributed to this report.