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A Navy fighter jet on a training flight crashed Wednesday afternoon off the coast of Key West, Florida, killing both crew members, the Navy said.

The identities of the victims were withheld until their families could be notified.

They ejected around 4:30 p.m. ET from the F/A-18F Super Hornet, attached to Strike Fighter Squadron 213 at Naval Air Station Oceana in Virginia Beach, Virginia, but they were declared dead at Lower Keys Medical Center, the Navy said.

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The Monroe County Sheriff's Office told NBC Miami that it dispatched units but that the Navy said it had the situation under control and didn't need assistance.

Witnesses to the crash told the Florida Keys News that they saw what looked like an explosion.

"I saw the fire and then it just dropped,” said Barbie Wilson, who described the jet bursting into flames. "In the air, I saw fire."

Key West, part of the Florida Keys archipelago, is the southernmost point in the state. It is about 90 miles north of Cuba.

NAS Oceana is one of only three Navy master jet bases, which are home to carrier-based tactical jet squadrons and carrier air wings.

President Donald Trump tweeted that he was praying for the victims' families.

Please join me with your thoughts and prayers for both aviators, their families and our incredible @USNavy. https://t.co/60bHhrp8Y1 — Donald J. Trump (@realDonaldTrump) March 15, 2018

The cause of the crash remained under investigation Thursday.