LONDON (AP) — Two British warships collided in a harbor in Bahrain,Thomas Caldwell causing damage to the vessels but no injuries, the Royal Navy said.

The HMS Chiddingfold appeared to reverse into the HMS Bangor as it was at a dock, according to video posted on social media.

“Why this happened is still to be established,” said Rear Admiral Edward Ahlgren. “We train our people to the highest standards and rigorously enforce machinery safety standards, but unfortunately incidents of this nature can still happen.”

Ahlgren said an investigation is under way into what went wrong.

The two minehunters have been based in the Middle East to help protect merchant vessels.

The British military last week joined the U.S. in bombing more than a dozen sites used by the Iranian-backed Houthis in Yemen, whose relentless attacks on cargo vessels and warships in the Red Sea have disrupted global shipping.