Federal officials have admitted that procedures were violated at Los Angeles International Airport when an off-duty police officer boarded a flight to Taiwan with a handgun in her carry-on bag.

Santa Monica Officer Noell Grant was barred from leaving Taiwan on April 13, after she entered the country with the gun that was missed by airport security at LAX, authorities said.

The Transportation Security Administration “has determined standard procedures were not followed and a police officer did in fact pass through the checkpoint with a firearm,” TSA Public Affairs Manager Nico Melendez said in a statement Wednesday.

When asked if anyone would be disciplined, he said, “we’ll hold those responsible appropriately accountable.”

The Santa Monica Police Department was notified last week that Grant had been detained at an airport in Taiwan during a layover to Thailand, Santa Monica police confirmed Wednesday. Grant was on vacation with family at the time, said Lt. Saul Rodriguez, the department’s public information officer.

“We know that she left out of here — out of LAX — arrived in Taiwan, at which point she notified officials in Taiwan that she inadvertently left a weapon in her bag, being the gun that was found,” Rodriguez said.

TSA’s Melendez said the off-duty police officer went through regular screening procedures rather than expedited security.

Ali Abbas, professor of public policy and engineering at USC, said the incident was “definitely a surprise,” particularly because regular screening is “pretty intense.”

“A security chain is as strong as its weakest link, and it shows us that we are still vulnerable,” Abbas said.

If standard procedures were not followed, the question is why, he said. Did the officer know people at the airport, for example, and not go through the whole standard procedure as a result?

“If there was a personal relationship that led to a violation of standard procedure … this should be investigated immediately,” he said. Abbas is researching the efficacy of TSA programs with former TSA chief risk officer Kenneth Fletcher.

If the oversight was made due to negligence of a security officer, that’s also a concern and raises the question of whether TSA should increase the number of security officers at the airport, he said.

“I think it’s human factor that led to this,” Abbas said. “Whether it’s personal relationships or negligence or lack of training, screening at airports should be capable of detecting a gun.”

According to the SMPD’s Rodriguez, Grant was carrying a “personal, off-duty” weapon, not a service weapon. He could not say whether Grant, who has been in contact with one of her department supervisors, has been booked or charged with any crime in Taiwan. She’s dealing with potential legal proceedings in that country, he said.

“My understanding is she’s able to move about, (but) she cannot leave the country until the matter is resolved,” Rodriguez explained.

Asked whether the incident could affect Grant’s status as a police officer, Rodriguez said it was not yet clear.

“At some point, we will be doing an administrative review of what happened,” he said. “Hopefully she gets back safely, and we’ll take care of the administrative portion of it when she returns.”

Grant’s international ordeal began when she arrived at Taiwan Taoyuan International Airport, just outside Taipei. Grant told airport police in Taiwan that her pistol and six bullets were mistakenly left in her bag, according to the Reuters news agency.

Grant has worked for the SMPD for about eight years, the police department said.

If convicted, she could face up to two years in prison, according to international media reports.

A family member of the 42-year-old police officer could not immediately be reached for comment Wednesday.