One of Britain’s newest Astute-class submarines has docked at Gibraltar after suffering a “glancing collision” with a merchant vessel, the UK Royal Navy announced, emphasizing that the HMS Ambush suffered “absolutely no damage” to her nuclear reactor.

The incident happened at around 1:30pm local time on Wednesday, when HMS Ambush was “submerged and conducting a training exercise” off Gibraltar, the Royal Navy said in a statement.

HMS Ambush before and after. pic.twitter.com/CdPQXhC9eb — James Doleman (@jamesdoleman) July 20, 2016

The Astute class nuclear submarine suffered “some external damage”, with the Royal Navy reassuring the public that “absolutely no damage” had been inflicted on its nuclear reactor.

The Navy also added that no one suffered in the incident, but the submarine had been forced to dock. “There are no safety concerns associated with HMS Ambush being alongside,” the Royal Navy stated.

The vessel ship that the submarine collided with suffered no damage, according to initial assessment. An investigation is now underway.

HMS Ambush struck one of tankers Vemaoil XXI, Vemaoil XXV or Eco Friend today at Gibraltar. pic.twitter.com/nqhA1i9xbR — SeaWaves Magazine (@seawaves_mag) July 20, 2016

The 7,400 ton and 97-meter-long nuclear submarine is equipped with torpedoes and Tomahawk cruise missiles. HMS Ambush is the first Astute-class and cost more than £1.1 billion ($1.46bn) to build.

On Wednesday the Royal Navy also said that it had been participating in drills in the Mediterranean aimed at “honing anti-submarine warfare capability.”

HMS Ocean leads international submarine hunting exercise https://t.co/h9WQZF3b2Jpic.twitter.com/nlM3OVik3y — Royal Navy (@RoyalNavy) July 20, 2016

“Ships and aircraft from the UK, US and France spent 10 days honing their ability to hunt submarines – a vital opportunity for all three nations to develop and practice their techniques as part of a maritime task group ... in the game of cat-and-mouse that is anti-submarine warfare,” the statement read.

On Thursday the Spanish government, which acknowledged it had been aware of the exercise, said that it wanted a full explanation.

The Spanish have long raise concerns over the presence of nuclear weapons near their territory.

Gibraltar is a small enclave on Spain’s southern tip that has been a British territory since 1713. Home to some 30,000, the enclave remains a source of British-Spanish tensions, with Madrid wanting to reassert its sovereignty.