The FBI has opened a criminal probe into allegations that a San Francisco sheriff’s deputy beat an inmate last week at County Jail No. 5 in San Bruno — the latest in a flood of alleged misconduct cases under investigation at the jail, officials said Tuesday.

The incident involved Deputy Alex Jayson, who is being investigated for punching inmate Deshaun Roberts in his housing pod on Thursday, officials said.

“We were asked to look into it, and we’re looking into it,” said Prentice Danner, a spokesman for the FBI’s field office in San Francisco.

Sheriff Vicki Hennessy asked the FBI to investigate the matter “in order to maintain public confidence in investigations,” said Nancy Crowley, a Sheriff’s Department spokeswoman.

“We take these things seriously,” Crowley said. “It went right up the chain of command and we responded immediately.”

Deputy Public Defender Chesa Boudin, who’s running for district attorney, alerted The Chronicle about the alleged beating but said he did not witness the incident. Several civilians in the jail, though, saw the incident, he said.

The alleged beating happened as Roberts was returning to his cell in between classes with the Five Keys Charter School, a nonprofit that teaches inmates in the jail, Boudin said.

Jail cameras captured the incident on video and sheriff’s officials began an internal investigation before contacting the FBI, Crowley said. Federal authorities are looking into whether Jayson committed a crime by depriving Roberts of his civil rights under the color of law, officials said.

Roberts, in jail on a first-degree robbery charge, has been moved to County Jail No. 4 in San Francisco, records show.

Jayson, who was assigned Friday to man the front gate on County Jail No. 5, has been placed in a new position where he does not have contact with the public, Crowley said. Jayson began his career at the department in May 2017 and recently came off a probationary period, officials said.

Ken Lomba, president of the Deputy Sheriffs’ Association, did not immediately respond to requests for comment.

The incident comes amid a spike in recent misconduct investigations at the jail that prompted members of the Board of Supervisors to call for more oversight of the Sheriff’s Department.

District 10 Supervisor Shamann Walton called a hearing last month to look into the reports of abuse and inquire about a botched internal investigation into “inmate fight club” allegations from 2015.

Additionally, the Sheriff’s Department has been investigating allegations that other deputies severely beat inmates and conducted degrading strip searches at County Jail No. 5 late last year.

The Sheriff’s Department forwarded some of the cases to the the city’s Department of Police Accountability, an independent oversight body created to investigate the Police Department.

Evan Sernoffsky is a San Francisco Chronicle staff writer. Email: esernoffsky@sfchronicle.com Twitter: @EvanSernoffsky