U.S. law enforcement agencies are investigating an alleged assassination threat against former President Donald Trump following a now-deleted social media post by former FBI Director James Comey, Homeland Security Secretary Kristi Noem said Thursday.

The post in question, shared on Instagram by Comey, featured an image of the numbers "86 47" spelled out in seashells. The number "86" is sometimes used as slang for "kill," while "47" refers to Trump, who is running to become the 47th president of the United States.

"Disgraced former FBI Director James Comey just called for the assassination of @POTUS Trump," Noem posted on X, formerly known as Twitter.

"DHS and Secret Service is investigating this threat and will respond appropriately," she said.

Comey responded in a follow-up Instagram post: "I posted a picture of some shells I saw today on a beach walk, which I assumed were a political message."

"I didn't realize some folks associate those numbers with violence. It never occurred to me but I oppose violence of any kind so I took the post down," he said.

Trump, who was wounded in the ear during an assassination attempt at a campaign rally in Butler, Pennsylvania, in July, has faced several threats throughout his political career.

Law enforcement officials have not confirmed whether charges will be filed. The Department of Homeland Security and U.S. Secret Service have not issued further statements as of Thursday afternoon.