Two more companies have been named as defendants in civil lawsuits involving a fatal explosion almost two years ago at the Victaulic plant in Lehigh County.

Inductortherm Corp., of Rancocas, N.J., and DISA Industries, of Oswego, Ill., were added today to separate suits filed in Northampton County Court.

The suits were filed last year by Richard and Brenda Geist of Alburtis, the parents of Bridgette Geist, the 37-year-old Walnutport woman who died in the explosion at the plant in Lower Macungie Township in April 2010, and her co-workers, Brian Diskin and Robert Motolese, who were injured.

As with the four other companies named in the suits, Inductotherm and DISA are accused of negligence in the design, construction and refurbishing of an inductor used in a furnace at the Victaulic plant.

The faulty inductor led to 9,000 pounds of molten metal and steam being ejected from the furnace, according to court documents.

The suits do not ask for specific amounts of damages.