A missile launched by a British nuclear submarine misfired and crashed into waters off the Florida coast last month, according to a report. The boosters on the Trident 2 missile—a projectile capable of delivering a nuclear warhead—failed to ignite, causing the missile to crash down into the Atlantic off Port Canaveral, according to The Sun. “It left the submarine but it just went plop, right next to them,” a source told the tabloid. Britain’s Defense Secretary Grant Schapps was allegedly on board HMS Vanguard at the time to witness the test. The missile, which was fitted with dummy warheads at the time, reportedly came within yards of the sub as it sank to the seabed, triggering an urgent search to recover the weapon and its sensitive technology. The U.K.’s defense ministry confirmed an “anomaly occurred” during the Florida exercise but insisted that Britain’s nuclear deterrent is still “effective.” The mishap follows another incident in 2016 in which another British submarine’s Trident missile launched off Florida malfunctioned and accidentally flew towards the U.S.