It is understood that Sandwell's interim leader, Councillor Maria Crompton, and Abbey councillor, Bob Piper, are being investigated by Sir Keir Starmer's party.
It is not yet clear why both councillors are under investigation. Both councillors Crompton, who also represents Tividale ward, and councillor Piper declined to comment. The Labour Party has been approached for comment.
Councillor Crompton has been a councillor for 17 years and became Sandwell's interim leader in July. Councillor Piper has been a councillor for 21 years.
They are councillor Joanne Hadley, cabinet member for safer communities, and Tipton ward councillor Ian Jones, who is a former cabinet member who has been a councillor for 22 years.
The suspension of councillor Hadley follows allegations of racism.
She did not respond to requests for a comment. Councillor Jones told the Express & Star that councillors "aren't able to comment on Labour Party business".
A Labour Party spokesperson said: "The Labour Party takes all complaints of racism extremely seriously and they are fully investigated in line with our rules and procedures, and any appropriate disciplinary action is taken."
The investigation into Councillor Crompton follows calls by Wednesbury North councillor Luke Giles for a "full investigation" into allegations of bullying within the Sandwell Labour Group. She declined to comment at the time.
Councillor Crompton became Sandwell's fourth leader since February 2019, when she took over the reins from councillor Yvonne Davies in July on an interim basis.
She became the second Sandwell Council leader to be suspended by the Labour Party in two years. It followed the suspension of Steve Eling, who was suspended by Labour in January 2019 following an undisclosed complaint. He subsequently stepped down as leader of Sandwell Council the following month in February 2019.
In May 2019, on the day Councillor Davies was elected as council leader, councillors Bill Cherrington and Julie Webb were kicked out of the Labour Party. That month, seven Sandwell councillors were also deselected by the Labour Party ahead of the local elections.