The New River Foundry’s parent company missed Friday’s deadline to respond to a proposed settlement of an $801,000 fine levied by the state after a Radford plant explosion killed three workers in March.

The Department of Labor and Industry will ask Michigan-based Intermet Corp. for an answer, spokeswoman Nancy Jakubec said Monday.

Debbie Sheppard, Karen Anderson Hamilton and Curtis Grooms died in the March 5 explosion that investigators said originated in the plant’s basement.

In September, Intermet was fined $801,000 for 31 safety violations investigators uncovered following the explosion at the New River Castings plant, now called the New River Foundry. The fine was the largest levied in the history of the Labor Department’s Occupational Safety and Health Compliance division.

Intermet contested the fine and last met with the state on Sept. 21, Kelly said.

The settlement agreement was offered by the state on Nov. 15, but the two sides haven’t met to discuss it.