CHARLESTON, W.Va. -- Institutional investors are continuing to target Massey Energy's board of directors over an explosion that killed 29 coal miners earlier this month.

The New Jersey Building Laborers Pension Fund blames Chairman Don Blankenship and other board members for the April 5 explosion at West Virginia's Upper Big Branch Mine. It sued them late last week in Delaware's Chancery Court.

Two other shareholders filed similar lawsuits last week in Wyoming Circuit Court in West Virginia: the International Union of Operating Engineers Pension Fund of Eastern Pennsylvania and Delaware, and the Louisiana Municipal Police Employees' Retirement System.

The Manville Personal Injury Settlement Trust was the first institutional investor to sue, April 15 in Kanawha Circuit Court. It also alleges these officials have violated the 2008 settlement of an earlier lawsuit filed over their management.

New York State Comptroller Thomas DiNapoli urged fellow shareholders on Tuesday to withhold their votes for directors Baxter Phillips, Richard Gabrys and Dan Moore when they're up for re-election at Massey's annual board meeting next month. DiNapoli oversees the New York State Common Retirement Fund, an investor, and earlier called for Blankenship to resign.

Board member Bobby Inman rejected shareholder allegations and criticisms during a Monday news conference held by Massey officials. Inman said these investors together hold about 2 percent of the company's 95 million or so outstanding shares.