It's being reported that vital equipment needed to rescue those on board the mini sub is waiting for the US authorities to clear the paperwork.
The Daily Mail has quoted an interview in US media earlier with David Concannon, who's an adviser to OceanGate, the company which is running the sub mission to view the wreck of the Titanic.
In it, he said vital equipment needed in the event of a rescue was on board a truck, waiting for the US authorities to approve its entry to America.
In an interview with NewsNation, a US TV channel, he says:
"This equipment has been on the tarmac for hours. When I communicate with the U.S. government, I get 'out of office' replies - not from everyone, but from key people that have a sign-off on this."
The Mail article shows a picture of heavy equipment on a Channel Seaways truck, but it's not known who that equipment is owned by, and why it's in the islands.
It's understood that five people are on board the small submersible, which is capable of diving deep enough to view the wreck, some 12,000 feet below sea level. One is British billionaire Hamish Harding.
The sub went missing on Sunday, early on in its mission. That has sparked a massive search mission involving aircraft and shipping.
Experts estimate the sub has around 72 hours of oxygen left from today (20 June) but they hope it has already surfaced. The Titanic sits around 400 miles away from the nearest land, St John's in Canada.