SPRINGBORO — General Dynamics Corp. has laid off 29 workers from its munitions plant on South Pioneer Boulevard, the company said Monday.

The defense contractor attributed the layoffs to a delay in an order for mortar fins from the U.S. Army. The 240,000-square-foot plant makes rocket motor tubes for the U.S. Army’s Hydra 70-air-to-ground rockets. The plant also produces liners and cartridges for 40mm ammunition rounds and components to its 60mm-120mm mortar rounds.

“Because of an unexpected delay in the U.S. Army’s 2013 order for 60mm and 81mm mortar fins, General Dynamics had to lay off 29 Springboro-operations employees today (Feb. 18),” said Karl Johnson, a spokesman for General Dynamics Armament and Technical Products. “We anticipate recalling the affected employees once the order is received.”

Johnson said the company is working with state unemployment officials to determine what benefits are available to employees, who were first notified of the layoffs Thursday. Affected employees did not report to work today, he said.

General Dynamics acquired the plant in August, seeing the facility as a good fit for the company. That’s still the case, Johnson said.

The acquisition was seen as a way for General Dynamics to consolidate its supply chain. The Springboro plant can perform metal forming, heat treatment, machining and coating, all under one roof. About 95 percent of the material it uses is aluminum.

“That still applies to the business,” Johnson said. “We have more products than the mortar fins. The Hydra is still an important part of the business.”

Johnson could not say when the Army’s order for mortar fins is expected or when workers may be recalled.

Asked if further layoffs are possible due to defense cuts or automatic across-the-board “sequestration” cuts, Johnson said, “We have no plan for further layoffs.”

When the company acquired the plant, it said 187 people worked there. Today, after the layoffs, the employee count stands at approximately 135. Johnson said “workload fluctuations” lowered the number of workers to about 165 before the layoffs.

This is the first round of layoffs General Dynamics has had at the facility, Johnson said.