A SANCTIONED unit of state conglomerate China Cosco Shipping Corp has denied accusations that the company’s tanker fleet has switched off their transponders to conceal the shipment of Iranian oils in violation of US sanctions.

The Reuters news agency cited two US officials as saying the US was “deeply concerned” about untrackable Chinese vessels carrying energy cargoes from Iran.

“None of our vessels had turned off the Automatic Identification Systems on board,” an official from Cosco Shipping Tanker (Dalian) told Lloyd’s List.

The company, also known as Dalian Tanker, is among the several Chinese firms and individuals that were blacklisted last month by the US over their alleged involvement in transporting Iranian oils via a complex ship-to-ship transfer logistics network used to obfuscate their origin and destination.

The Cosco official added that an earlier Reuters report — which said 14 Dalian Tanker vessels stopped sending location data from their AIS between September 30 and October 7 — was incorrect.

“We’ve sent Reuters photos from the vessels to prove that we didn’t shut off the AIS. And our vessels have not shipped oils from Iran,” the official said.

In a written statement, the company blamed technological issues for the missing of its vessel traces.

It said the shore-based receiving stations normally can only reach AIS signals within 50 nautical miles offshore or even shorter during bad weather, and hence cannot locate ships sailing further away from the coast.

While low-orbit satellites were now used to supplement the AIS signals of ships in open sea, the massive coverage areas and the enormous number of vessels have resulted in a high error rate of the information, the statement added.

“These have led to the misunderstanding that the suspected ship has closed AIS or the ship’s position is not updated in time.”

According to the report, two Dalian Tanker very large crude carriers — Yuan Shan Hu and Cosglad Lake — were untraceable between October 8 and October 16, while the location of aframax tanker Yang Mei Hu has been lost since October 11.

Yuan Shan Hu last appeared on Lloyd’s List Intelligence vessel tracking data on October 10 near the port of Qingdao, China, while Cosglad Lake was in the Addaman Sea, west of Myanmar, on October 14. Yang Mei Hu was about 25 nautical miles away from the anchorage of China’s Ningbo port on October 15.

As of end-June, Dalian Tanker and its subsidiaries owned 43 tankers, including 26 very large crude carriers and three suezmaxes, according two disclosure documents released by Dalian Tanker's parent company Cosco Shipping Energy Transportation on October 1.