Drugstore giant Walgreen Co. sued former laboratory-testing partner Theranos Inc. in a federal court in Delaware, alleging it breached a contract between the two companies.

The Walgreens Boots Alliance Inc. unit is seeking $140 million in damages, equal to the amount it invested in Theranos, according to people familiar with the matter.

The civil suit was filed under seal, so few details about the allegations were disclosed in court records. The people familiar with the matter said Walgreens claims it was misled by Theranos about the state of its technology when the two companies forged their agreement.

In a statement, Theranos said it is “disappointed” that Walgreens filed the lawsuit. “Over the years, Walgreens consistently failed to meet its commitments to Theranos. Through its mishandling of our partnership and now this lawsuit, Walgreens has caused Theranos and its investors significant harm.”

Theranos said it “will respond vigorously to Walgreens’ unfounded allegations, and will seek to hold Walgreens responsible for the damage it has caused to Theranos and its investors.”