LONDON — Two RAF Tornado jets crashed Tuesday on Scotland’s coast, leaving two British airmen missing after two others were plucked from the sea by helicopter.

It was not clear if the jets crashed into each other. The search for the two missing airmen and the wreckage was continuing, British officials said.

The Ministry of Defense said the GR4 Tornado jets from RAF Lossiemouth were flying in the Mornay Firth area in eastern Scotland when contact with them was lost. Group Capt. Ian Gale, the station commander at RAF Lossiemouth, confirmed “with great regret” the crash of two of his station’s Tornado G4 aircraft and said four aircrew were involved.

“The circumstances remain uncertain but clearly this is a very serious incident,” he said in a statement. He would not speculate on what caused the crash.

Richard Smith of the Royal National Lifeboat Institution said the two pulled from the sea had been sent to Raigmore Hospital in Inverness.

“Rescue operations are continuing and I would like to record my gratitude for the ongoing efforts of all those involved,” Gale said, adding that his thoughts are with the families and friends of those involved.

About 15 volunteers in three lifeboats joined the rescue operation after reports that two jets came down about 25 miles (40 kilometers) south of Wick.

The Royal Air Force operates Tornado GR4’s from two bases — RAF Lossiemouth in Scotland and RAF Marham in England. The Tornados are two-seaters and described as “all-weather attack aircraft” capable of low-level supersonic flight.

It’s not the first time Tornados have run into trouble in Scotland in recent years. Last January, two crew from RAF Lossiemouth were rescued after their Tornado GR4 crashed into the sea off the west coast of Scotland.

The aircraft most recently saw action with the RAF over Libya and has also been used in Iraq and Afghanistan.

They are not part of the Ministry of Defense’s multi-tiered defense plan for the upcoming London Olympics, which will depend on Typhoon jets to be used in London airspace.