BEIJING (Reuters) - China’s top anti-graft watchdog announced on Monday an investigation into one of its own former senior inspectors, as the body ramps up a campaign to expose corruption in its own ranks.

Chinese President Xi Jinping has waged war on graft for over four years, vowing to continue until he has cleared the ruling Communist Party of both high and low-level graft, which he warns could threaten the party’s existence if left unchecked.

Inspection teams have been a core feature of the campaign, parachuted by central authorities into provinces or institutions to tackle entrenched corruption, in theory immune from bribery and pressure by local officials.

The Central Commission for Discipline Inspection (CCDI) said in a online statement on its website that a vice-ministerial level inspector from the Central Inspection Team, Zhang Huawei, was under investigation for suspected “serious disciplinary violations”, a common euphemism for graft.

Zhang could not be reached for comment.

The CCDI has in recent months made efforts to show it is serious about tackling corruption within its own ranks, which it refers to as “darkness hiding beneath the light.”

The CCDI began 2017 by airing a three-part television series focusing on cases where graft-busters had been caught on the take and releasing a new series of rules to guard against abuses of power by disciplinary officials.

The drive by CCDI to “clean ones own doorstep” comes as Beijing mulls sweeping changes to its anti-graft architecture to create a National Supervision Commission, set to incorporate various corruption-fighting bodies in a powerful single entity.

The move could also be used as a way for Xi to justify retaining top graftbuster Wang Qishan in a central leadership position beyond the usual retirement age at an upcoming leadership reshuffle late this year.