Electric-vehicle maker Workhorse Group is protesting the U.S. Postal Service’s decision to award a lucrative contract to build the mail carrier’s next-gen delivery truck to Wisconsin-based Oshkosh Defense.

What’s contained in the bid protest complaint filed with the U.S. Federal Court of Claims is unknown, however, because it was filed under seal.

A motion filed with the complaint states it contains confidential and proprietary information, “the public release of which would cause severe competitive harm.” The Cincinnati-area company with ties to Lordstown Motors Corp. also argues the complaint contains information subject to a nondisclosure agreement with the postal service.

The company in a news release did not provide more details, but stated it would provide updates when appropriate and permitted under the nondisclosure agreement.

Workhorse also filed a redacted, but still sealed version of the complaint, and asked the court keep it sealed until attorneys for both sides can agree on a public copy, the motion states.

U.S. Postmaster Louis DeJoy in February announced that Oshkosh Defense, a division of Oshkosh Corp., won the 10-year contract worth about $6 billion to make up to 165,000 new delivery trucks for the postal service. Ten percent of the vehicles would be battery-powered; the rest would be equipped with fuel-efficient internal combustion engines, according to DeJoy.

According to a Reuters report, DeJoy in March stated in a letter to lawmakers that with the government’s help, the postal service could commit to making most of the fleet electric within a decade. DeJoy added the postal service needs about $8 billion to electrify the new fleet to the “maximum extent” feasible.

Last month, the U.S. House oversight and reform committee voted to authorize $8 billion for the postal service, according to Reuters.

Workhorse was among the finalists vying for the contract. In March company executives met with postal service officials to discuss the award and further specifics on the postal service’s selection process but is prevented from disclosing the details.

In the wake of the announcement, a group of U.S. lawmakers from Ohio, including Democratic Congressman Tim Ryan of Howland, urged President Joe Biden to halt the contract award until it could be reviewed.

Ryan also co-sponsored a resolution in the House asking the same. He also called on the U.S. Securities and Exchange Commission to investigate a large purchase of Oshkosh stock less than one day before DeJoy’s announcement.

Workhorse holds a 10 percent stake in Lordstown Motors. Its factory in Lordstown, the former General Motors assembly plant, likely was the location to manufacture the Workhorse delivery trucks.

Lordstown Motors underwent a major shakeup Monday with the resignations of founder / CEO Steve Burns and Chief Financial Officer Julio Rodriguez. The company also acknowledged some inaccurate statements were made about preorders for the company’s electric truck, the Endurance, limited production of which is expected to launch in September.

Shares in Workhorse traded down 3 percent Thursday to close at $14.45 per share. The stock was up with news of the complaint Wednesday.