The administration of US President Donald Trump is considering closing down the recently re-opened US embassy in Havana after several American diplomats experienced a string of unexplained health problems.

We have it under evaluation, Secretary of State Rex Tillerson said on Sunday. It’s a very serious issue with respect to the harm that certain individuals have suffered. We’ve brought some of those people home. It’s under review.

The US intelligence community has not yet managed to come up with a clear explanation as to what, or who caused mysterious injuries reported by 21 US diplomatic staff in Cuba.

Some of them have permanent hearing loss or concussions, while others suffered nausea, headaches and ear-ringing. Some are struggling with concentration or common word recall.

An ongoing probe has baffled the investigators who initially thought the injuries could have been caused by a sonic weapon, VICE News reported Saturday.

None of this has a reasonable explanation, said Fulton Armstrong, a former CIA official who served in Havana before the US re-opened an embassy there. It’s just mystery after mystery after mystery.

Tillerson has called the events health attacks but the State Department has described them as incidents while acknowledging the US still does not know what has occurred.

On Friday, five Republican senators wrote Tillerson calling on him to not only close the embassy, but also expel all Cuban diplomats from the US.

Cuba’s neglect of its duty to protect our diplomats and their families cannot go unchallenged, said two senators -- Tom Cotton of Arkansas, Marco Rubio of Florida.

Former US President Barack Obama re-established diplomatic relations with Havana in 2015 and loosened some restrictions on doing business in the country during his tenure in the White House.

During last year’s presidential campaign, Donald Trump threatened to terminate deals that the Obama administration made with Cuba.

President Trump is now reportedly considering sanctions against Cuba in a bid to scale back Obama’s policy shift towards the southern neighbor.