WASHINGTON (AP) — When a Russian fighter jet collided with a large U.S. surveillance drone over the Black Sea on Tuesday, it was a rare but serious incident that triggered a U.S. diplomatic protest and raised concerns about the possibility Russia could recover sensitive technology.

U.S. and Russian officials had conflicting accounts of the collision between the MQ-9 Reaper drone and the Russian Su-27 fighter jet — each blaming the other. But a Pentagon spokesman raised the possibility that the Defense Department could eventually declassify and release video it has of the collision.

Defense officials said the drone has not been recovered. But the Pentagon declined to say whether any effort was underway to gather debris or pieces of the Reaper.

Here’s what’s known — and uncertain — about the crash.

WHAT THE US SAYS HAPPENED

The Pentagon and U.S. European Command said that two Russian Su-27 aircraft dumped fuel on the MQ-9, which was conducting a routine surveillance mission over the Black Sea in international airspace. They said the Russian jets flew around and in front of the drone several times for 30 to 40 minutes, and then one of the Russian aircraft “struck the propeller of the MQ-9, causing U.S. forces to have to bring the MQ-9 down in international waters.”

Air Force Gen. James Hecker, commander of U.S. Air Forces Europe and Africa, said that the Russian jet’s actions “nearly caused both aircraft to crash.” Pentagon spokesman Brig. Gen. Pat Ryder said the collision likely also damaged the Russian fighter jet, but the Su-27 was able to land. He would not say where it landed.

The Pentagon said the drone was “well clear” of any Ukrainian territory, but did not provide details. A U.S. defense official said it was operating west of Crimea over the Black Sea. The official spoke on condition of anonymity to provide mission details.

It’s not clear if the collision was an accident or intentional, but both sides agree the Russian aircraft were trying to intercept the drone.

WHAT RUSSIA SAYS HAPPENED

The Russian Defense Ministry said the U.S. drone was flying near the Russian border and intruded in an area that was declared off limits by Russian authorities. It said that the Russian military scrambled fighters to intercept the U.S. drone. It claimed that “as a result of sharp maneuver, the U.S. drone went into uncontrollable flight with a loss of altitude and collided with water surface.”