House Democrats are opening an investigation of the Trump White House’s security clearance practices and what they are calling “grave breaches” of procedure that allowed potentially compromised people to access the country’s most sensitive secrets.

The investigation, announced Wednesday by House Oversight and Government Reform Committee Chairman Rep. Elijah E. Cummings (D-Md.), seeks both to expose why the White House allowed certain people with security clearance issues to continue to access sensitive information and to close those loopholes.

The panel also plans to challenge administration officials on why they have not been more responsive to congressional requests regarding the security clearance process, as required by law.

Among the people whose cases the panel plans to scrutinize are former national security adviser Michael T. Flynn, who recently pleaded guilty to lying to the FBI about his contacts with Russian officials; Trump’s son-in-law and senior adviser, Jared Kushner, who did not disclose several contacts with foreign officials on his security clearance forms; and former White House staff secretary Rob Porter, who was accused of spousal abuse.

Over the course of Trump’s presidency, the committee’s Democrats have sent letters to the administration asking for information regarding the security clearances of officials who were shown to have problems on their application forms or who were operating on interim clearances for abnormally long periods, and why the White House had not revoked the clearances of people who engaged in conduct that could have compromised their fitness to have access to sensitive information.

In a Wednesday letter to White House lawyer Pat Cipolline, Cummings reminded him that the White House had already acknowledged it needed to make adjustments.

“Last year, General John Kelly, President Trump’s Chief of Staff at the time, conceded that there are major ‘shortcomings’ with the White House’s security clearance process. He warned that the White House ‘should — and in the future, must — do better,’ ” Cummings wrote, adding: “I agree.”

The investigation will focus not just on Trump’s time in the White House, but also on actions of his transition team, members of which also handled sensitive information with questionable clearances. Vice President Pence, who was chair of the transition team, received Cummings’ letter, as did the FBI, the State Department and the National Rifle Association.

House Democrats are interested in learning whether security officials limited, suspended or turned down any White House staffers’ applications to acquire permanent security clearances — a request that could disclose why the intelligence community never approved Kushner to view highly “sensitive compartmented information” despite his proximity to the president.

Other figures of note who are expected to be scrutinized under the probe include Flynn’s son and transition team member, Michael Flynn Jr.; his former deputy, K.T. McFarland; his former Africa director, Robin Townley; and his eventual successor, John Bolton. Sebastian Gorka, the onetime deputy assistant to the president whose security clearance Kelly reportedly revoked, is also a subject of the probe.

Cummings did not include in his letter any pledge to investigate Trump’s pledge last summer to revoke the security clearance of former CIA director John Brennan, who has frequently criticized the president’s policies on television and Twitter.