Commerce Secretary John Bryson underwent more medical tests in Washington on Tuesday as doctors looked for the cause of a seizure he suffered while driving on Saturday in California.

Bryson, 68, announced Monday night that he is taking a leave of absence for health reasons. On Tuesday, he spoke for the first time with President Obama. A White House spokesman said the president called Bryson and told him to “focus his thoughts on his own health and his own family.”

About 5 p.m. Saturday, Bryson’s Lexus allegedly collided with two other vehicles in the Los Angeles suburbs — striking one of the vehicles twice. Nobody in the other vehicles was seriously hurt.

Bryson was found unconscious after a third crash and was later cited for a felony hit-and-run. Police said they did not find any indications that drugs or alcohol were a factor in the collisions. Prosecutors must now decide whether he will be charged.

On Tuesday, Rebecca Blank — Bryson’s deputy, who is serving as acting secretary during his leave — took Bryson’s place at a meeting of the U.S. India Business Council. According to her prepared remarks, Blank said that Bryson “regrets that he could not be here today and sends his greetings.”

Bryson’s aides offered no new details about the cause of Bryson’s seizure or the role it played in the crashes. Police said Bryson struck a Buick, got out to speak with its occupants, returned to his car and hit the vehicle again as he pulled away.

About five minutes later, police said, he struck another car. First responders found him unconscious behind the wheel.

Doctors say that one type of seizure — a “partial complex seizure” — can cause abnormal electrical activity in just one part of the brain. That would allow a person to continue performing simple tasks but leave them unable to complete more complex activities.

Bryson had gone to California to give a commencement address last Thursday at the Polytechnic School in Pasadena, from which his children had graduated. That was his last public event before the crashes, which occurred when Bryson was alone and not on official business.

Two parents who attended the graduation said that Bryson gave an emotional speech that encouraged graduates to embrace diversity and service and to keep their sense of curiosity.

But the parents said that his demeanor seemed unusual: He took long pauses, mispronounced several words and spoke in a flat tone. They said that attendees at the event remarked afterward that Bryson seemed “off.”

“At times it seemed like he was laboring or hunting for a word, and maybe even mispronouncing a word, slurring a word,” said Tim Genske, a real estate broker from Altadena, Calif., whose daughter was graduating.

“It seemed like he was laboring harder than someone would who’s spoken hundreds or thousands of times” at similar events, Genske said.

Concerns about Bryson’s demeanor on Thursday were first reported by the Los Angeles Times.

Staff writer David Brown and research editor Alice Crites contributed to this report.