The Strait of Hormuz appeared to remain largely blocked on April 8, as shipowners try to understand if they can safely transit the vital waterway following a ceasefire between the U.S. and Iran that was announced overnight.

Just three ships were observed leaving the region on April 7, according to ship-tracking data compiled by Bloomberg. Some had links to Iran, and the country’s media subsequently reported that passage for tankers will remain blocked after attacks on Lebanon. In normal times about 135 ships cross daily, and more than 800 freighters are stuck inside the gulf, mostly waiting to leave.

While shipowners and insurer groups lined up to welcome the ceasefire, they also warned that more details will be needed to determine if safe transit is possible. Iran has said a precondition of the ceasefire is that its armed forces should coordinate navigation through what is the world’s most important oil channel. Tehran has also been charging a toll of as much as $2 million a transit for some carriers.

“Time will tell whether it is a pause or a peace but, in the meantime, it is highly unlikely that trade into the Gulf will simply resume,” said Neil Roberts, head of marine and aviation at the Lloyd’s Market Association. “The region remains at heightened risk with none of the underlying tensions resolved.”

Ships of all types were seen on the morning of April 8, clustered on either side of Hormuz, around Dubai in the Persian Gulf and Khor Fakkan in the Gulf of Oman.

While owners publicly and privately expressed cautious optimism, they added that it still isn’t clear how transits will work in practice. 

A.P. Moller-Maersk A/S, the world’s second-largest container line, said the pause “may create transit opportunities, but it does not yet provide full maritime certainty.” Japan’s NYK said it was monitoring the situation. 

Bimco, a shipping trade group whose members control almost two-thirds of the world’s seaborne freight capacity, also struck a cautious tone, adding that it was still awaiting the details of safe navigation plans from the U.S. and Iran.

“Leaving the Persian Gulf without prior coordination with the U.S. and Iran would entail heightened risk and would not be advisable,” said Jakob Larsen, the group’s chief safety and security officer.

Those views mirrored private comments from owners with ships in the region. 

Several in Asia, the Middle East and Europe said they were calling insurers and security advisors, and had put vessels on standby to transit Hormuz. 

How soon flows return to normal will dictate the path ahead for global commodity prices. 

The waterway, which handles a fifth of the world’s oil and liquefied natural gas, has been all but closed since U.S. and Israeli strikes at the end of February prompted Iran to tighten its control, triggering an unprecedented oil-supply crunch. 

Throughout the conflict shipowners have cited the safety of their crews as a reason not to transit.

Shipowners, brokers and insurers also pointed to what they said were several apparently different versions of Iran’s peace plan as one reason for a lack of clarity. 

Iran says it has agreed to two weeks of safe passage in coordination with its armed forces and within “technical limitations.”

By contrast, U.S. President Donald Trump announced a “COMPLETE, IMMEDIATE, and SAFE OPENING.” He said in a separate social-media post that the U.S. would be “helping with the traffic build up” and “hangin’ around” to ensure smooth flows, options unlikely to appeal to Tehran.

“You don’t switch global shipping flows back on in 24 hours,” said Jennifer Parker, adjunct professor at the University of Western Australia Defence and Security Institute. “Tanker owners, insurers and crews need to believe the risk has actually reduced — not just paused.”

Ships that transport energy make up a large part of the fleet that’s stuck inside the gulf, data from intelligence firm Kpler show. There are currently 426 tankers hauling crude oil and clean fuels, plus 34 liquefied petroleum gas carriers and 19 liquefied natural gas vessels. The remainder are carrying dry commodities, like agricultural or metal products, or containers.

Traders and shipowners will now be closely monitoring which ships start making their way to transit the strait in either direction, and how they fare. As of the morning of April 8, more than 1,000 vessels are waiting on both sides, in clusters around Dubai and Khor Fakkan, in the Gulf of Oman.

The first two ships to attempt an exit since the announcement appeared to be sailing as a pair toward Iran’s Larak and Qeshm islands — an area dubbed by the shipping industry as the Iranian tollbooth — on the morning of April 8, ship-tracking data show. One of them is the Tour 2, a U.S.-sanctioned oil tanker that’s flagged to Iran. 

Sailing next to the tanker is a Greek-owned bulk carrier, NJ Earth, whose voyage history within the Persian Gulf suggests either spoofing to hide location, or interference by electronic warfare. There were no contact details listed on database Equasis for its owner, NJ Earth Marine Ltd., and manager, NJ Trust Marine Ltd. 

“It’s good to see that the market is reacting the way it is, but this is day one of a tentative ceasefire,” Michael Pregent, a former U.S. Intelligence advisor, told Bloomberg Television. “We are likely to see the regime control who moves through, who is charged what, and who is denied.”

Movement of LNG ships will also be particularly closely monitored, as no loaded carrier has made it through the strait since the war began and one recent attempted transit by two tankers ended in a last-minute U-turn. About 20% of global LNG traffic went through Hormuz last year.

According to an International Maritime Organization tally at end March, some 20,000 civilian seafarers are stuck on board trapped ships and the other utility and support vessels. Those crew members have been facing dwindling supplies, fatigue and psychological stress, the United Nations agency warned.

The IMO said on April 8 that it welcomed the agreement.

“I am already working with the relevant parties to implement an appropriate mechanism to ensure the safe transit of ships through the Strait of Hormuz,” Secretary-General Arsenio Dominguez. “The priority now is to ensure an evacuation that guarantees the safety of navigation.”