The images from Planet Labs obtained by The Associated Press have the Adrian Darya-1 still near the port city of Tartus. The images taken Sunday show another smaller vessel nearby.
The Adrian Darya 1, formerly known as the Grace 1, was carrying 2.1 million barrels of Iranian crude oil worth some $130 million.
Britain, meanwhile, said Tuesday it's clear the tanker delivered its cargo to Syria in violation of international sanctions.
The Foreign Office said Iran's ambassador to the U.K. has been summoned for a dressing-down by Foreign Secretary Dominic Raab.
Raab said in a statement that Iran had broken a promise that oil aboard the Adrian Darya 1 would not go to Syria.
"This sale of oil to Assad's brutal regime is part of a pattern of behavior by the government of Iran designed to disrupt regional security," he said. "This includes illegally supplying weapons to Houthi insurgents in Yemen, support for Hezbollah terrorists and most recently its attempts to hijack commercial ships passing through the Gulf.
"We want Iran to come in from the cold but the only way to do that is to keep its word and comply with the rules based international system."
Iranian Foreign Ministry Abbas Mousavi has been quoted saying the ship has unloaded its cargo, without elaborating.
Gibraltar earlier seized and held the tanker for weeks on suspicion of the tanker breaking European Union sanctions on Syria. The British territory later released the vessel after authorities there said Iran promised the oil wouldn't go to Syria.