The Biden administration said Tuesday it has not uncovered any evidence three unidentified flying objects shot down over the weekend over North American territory are connected to a Chinese — or any other nation’s — surveillance program. National Security Council spokesperson John Kirby said the objects could turn out to be related to commercial or research efforts.

Bloomberg reports the Raytheon-produced missiles used by the U.S. to shoot down the objects come at a cost of around $440,000 each.