After the seizure of a Western cargo ship by the Iranian military in international waters on Tuesday, shipping experts said Iran's actions could destabilize its international relations if repeated.
The Maersk Tigris, which was carrying general cargo, was seized by the Iranian navy while it transited the Strait of Hormuz en route to Jebel Ali in the United Arab Emirates (UAE) from Jeddah in Saudi Arabia. It was still under Iranian control on Wednesday.
Iranian forces seized the Marshall Islands-flagged ship after firing warning shots across its bow and ordering it deeper into Iranian waters, the U.S. Pentagon said on Tuesday.
Maersk Line reported on Wednesday that it thought the boat was being escorted towards Bandar Abbas in Iran by Iranian patrol boats.
Of the 30 or so crew members on board, none are believed to be Americans, according to the Pentagon.
"The crew is safe and under the circumstances in good spirits," said Maersk Line Senior Press Officer Michael Christian Storgaard in a statement on Wednesday. "The well-being of the crew remains our paramount concern."
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It is unknown, however, when the ship and its crew will be released, a spokesman for Rickmers Shipmanagement, the company which manages and crews the Maersk Tigris, told CNBC on Wednesday.
"The last update, we had a few hours ago," said Spokesman Cor Radings said.
"The crew are safe on board in reasonably good health. Our objective is to get a swift release of the ship and its crew and we are still trying to seek clarification as to why the ship was seized in the first place," he later added.
The seizure risks becoming a major international spat, at a time when Iran is in delicate negotiations with Western powers for sanctions to be dropped in exchange for a halt to its nuclear enrichment program.
The Pentagon saying it is monitoring the seizure situation and U.S. officials have branded the Iranian action as "inappropriate," according to various media reports.
The Strait of Hormuz is in Iranian territorial waters, within 12 miles of the Iranian coast, but is recognized as containing international shipping lanes, according to the Pentagon. This means that the principle of "innocent passage" should be applied, meaning that law-abiding foreign ships should be allowed to pass, the Pentagon said.
Danish-owned Maersk Line said it had contacted Iranian authorities and been told that the seizure was "related to an allegedly unresolved cargo claim."
"We have however not received any written notification or similar pertaining to the claim or the seizure of the vessel," said Maersk Line's Storgaard in a news statement on Wednesday.
"We are therefore not able to confirm whether or not this is the actual reason behind the seizure. We will continue our efforts to obtain more information."
However, Iran's Fars news agency reported that "the vessel had been seized for trespassing on Iran's territorial waters in the Persian Gulf."
One maritime expert following the situation, who preferred not to be named, said the seizure was a diplomatic rather than shipping issue.
"It's not a legitimate argument that the Iranians are using to say that arresting a vessel at sea is normal procedure. If a vessel is arrested it would usually always happen in a port, rather than at sea," the expert told CNBC on Wednesday.
The expert said that while a lot of detail had yet to emerge about the seizure, he found it "hard to believe" that it was due to a "civil matter," as Iranian officials were reported to have said on Tuesday.
"It's certainly not normal practice to go around arresting vessels like that," the expert added.
The shipping lane where the Maersk Tigris was stopped is one the busiest shipping lanes in the world, making Iran's actions more surprising, given that disruptions to cargo containers could have an impact on global trade and diplomatic relations.
Albert Stein, managing director of AlixPartners, which compiles an annual shipping industry outlook report, told CNBC on Wednesday that Iran's action was a one-off—but the country could be playing with fire.
"This is one ship and it looks like a one-off, but if this is repeated then there will be a much bigger problem for everyone. But from a shipping industry perspective, we certainly haven't seen much movement in the insurance rates for the Straits of Hormuz."
He forecast the ship would be released fairly soon and said that most ship owners would not be put off using the Straits of Hormuz, given that the passage was a key trading route. "Frankly, they don't have much of a choice," he said, with the Middle East reliant on that lane for its goods.
Around 90 percent of the world's goods are still transported by ship, according to the International Maritime Organization.
The shipping industry certainly does not need any more turbulence at the moment. The Baltic Dry Index, which measures the cost of transporting major materials by sea and is seen as a key indicator of global demand, is hovering around 600, far below the 1,484 level of last November.
Nigel Gardiner, managing director for maritime research at Drewry Shipping Consultants, told CNBC on Wednesday that nothing would be gained from Iran disrupting the flow of traffic in the Straits of Hormuz.
"The Straits of Hormuz is one of the busiest shipping lanes in the world and it's in a very sensitive political area so it's very important that ships are able to move freely through that area," Gardiner told CNBC Wednesday. "There's nothing to be gained from stopping shipping through there."
The capture of the vessel en route from Saudi Arabia comes at a time of increased tensions between Riyadh and Tehran, after Saudi Arabia launched a bombing campaign against neighboring Yemen, where Iran has reportedly back a rebel uprising rebels. Iran denied this.