Small Iranian "ghost fleet" tankers are slipping past the U.S. naval blockade and smuggling sanctioned liquefied petroleum gas (LPG) to China through a shadowy maritime hub off Malaysia, according to U.S. investigators who covertly filmed one of the vessels en route in September.

"This tanker had loaded its Iranian LPG from Assaluyeh Port, Iran, in late August. It then breached the U.S. blockade and made its way to a Malaysian anchorage," Jemima Shelley, a senior analyst at UANI, explained.

"What this shows us is that some vessels are managing to breach the U.S. maritime blockade," Shelley said of the footage shared exclusively with Fox News Digital.

"Most vessels aren't, but since the reinstatement in mid-July, we have seen only nine small tankers being successful in their breach of the U.S. blockade and departing the Gulf of Oman laden with oil or LPG."

At the center of the operation is the Malaysian Eastern Outer Port Limits Anchorage, known as the EOPL, an offshore shipping area approximately 70 kilometers from Malaysia’s coastline.

The anchorage has become a critical staging ground for Iran’s sanctioned energy trade with China, Shelley said.

The area allows vessels to wait offshore, receive supplies and transfer cargo between tankers, providing a logistical lifeline for Iranian energy exports as American naval forces patrol waters closer to Iran.

UANI had been monitoring the SOGL before its arrival in Malaysian waters, Shelley explained.

"On September 16th, United Against Nuclear Iran chartered a supply vessel and transited 100 nautical miles into the Malaysian Eastern Outer Port Limits Anchorage," Shelley said.

"Here we witnessed firsthand the illicit activities of ghost fleet tankers, as well as some Iran-flagged cargo ships that were located in this anchorage, one of them being the SOGL."

She described the SOGL as "a Handymax small tanker that was laden with 500,000 barrels of Iranian LPG."

The U.S. maritime blockade was first imposed April 13, temporarily lifted in mid-June and reinstated July 14 after diplomatic negotiations collapsed. The operation has largely stopped Iran from exporting crude oil, depriving Tehran of a major source of revenue as the country faces intense economic pressure.

"The U.S. blockade is an overwhelming success at preventing vessels laden with Iranian oil and petrochemicals from leaving the Gulf of Oman," Shelley said.

She added that since the blockade was reinstated, "no Iranian crude oil has managed to depart and be a successful export for Iran, which is a huge economic pressure for the Iranian regime."

"It's just that there are some opportunistic small tankers that are just managing to breach the blockade."

The United States, she said, is primarily prioritizing Iranian crude and very large tankers, which often carry "two million barrels of Iranian crude."

LPG is a flammable mixture of hydrocarbons, primarily propane and butane, used for heating, cooking, transportation and industrial production.

"LPG carries a lot of risks," Shelley said. "The U.S. blockade's first course of action is to try to attempt to turn around these vessels, which is their main technique for enforcing the U.S. blockade."

"However, sometimes they do have to use military force and this would be incredibly high risk on far more volatile cargo such as LPG."

According to Shelley, the smaller vessels exploit those challenges while using tactics commonly associated with Iran’s ghost fleet.

"So what they'll do is they will turn off their AIS. They will often fly a false flag so they're completely stateless vessels," she added.

The SOGL, identified by IMO number 9208227, was added to the U.S. Treasury Department’s Iran's oil trade to China," Shelley said.

"It is used by ghost fleet tankers, Iran-flagged tankers that will load Iranian crude and then transit eastwards from Iran all the way to this anchorage where they will often conduct ship-to-ship transfers with the final tanker bound for China."

"Often this anchorage is also used for floating storage, which is how Iran managed to survive for so long with the U.S. blockade being reinstated in July," Shelley said.

She also clarified that since the blockade has been enforced, Iranian floating storage has fallen to "zero to seven million barrels."

"So you can see how they have survived from having this offshore anchorage where illicit ghost fleet tankers have been able to wait laden with Iranian products."

UANI’s video also shows the SOGL sitting low in the water and receiving bunkering services from a smaller tanker off Malaysia, where Shelley said authorities appear to be "looking the other way."

"This is a common thing that you will see in this anchorage, because not only is this anchorage used for ship-to-ship transfers, but also these ghost fleet tankers, as well as some cargo ships in this anchorage, require various services, whether that is food, logistics or bunker fuel."

China is the dominant destination for Iranian oil and LPG, providing Tehran with a critical economic outlet despite U.S. sanctions and the naval blockade.

"For years, China has made up 80% of Iran's liquid cargo exports, and we have seen that only grow since the beginning of the Iran War. Now China is importing almost 100% of Iran's oil and LPG exports."

"It has created a system and trade that has allowed Iran to avoid sanctions, U.S. and OPEC sanctions, whilst China is able to buy highly discounted Iranian oil and LPG."

"After United Against Nuclear Iran's trip to the EOPL, interestingly, this small LPG tanker SOGL did not conduct a ship-to-ship transfer," Shelley said.

"Instead, it transited northbound into the South China Sea, where it finally discharged its Iranian LPG at Xinzhou Port in China."

The G Summer, a U.S.-sanctioned LPG carrier with a capacity of approximately 7,000 cubic meters, was also separately tracked transmitting signals from the Arabian Sea beyond the American blockade line in April, according to Bloomberg.

The vessel broadcast a message indicating it had an "all Chinese crew" aboard, while shipping analytics identified Iran as its last cargo country and Galle, Sri Lanka, as its reported destination.

Fox News Digital has reached out to CENTCOM for comment.