The California Public Employees’ Retirement System is questioning United Health Group about $2.4 billion in stock options the company granted its top executives, according to a published report.

The pension fund, known as Calpers, sent UnitedHealth a letter requesting a meeting with its executives before the company’s shareholder vote May 2, says a report by Bloomberg News. Calpers warned it may withhold its proxy votes for the company’s chief executive, William W. McGuire, who will receive $1.6 billion in options, according to Bloomberg.

The challenge comes a week after Minnesota’s attorney general filed a lawsuit against UnitedHealth, Minnetonka, Minn., over the same stock options.

The Minnesota lawsuit claims UnitedHealth backdated stock options to allow top executives to buy shares at below fair market value, according to the report.

The company recently reported first quarter earnings of almost $1.5 billion on revenues of $17.6 billion, up from $1.2 billion on $11.2 billion in revenue for the same period the year before.