No oil tankers have left Iranian loading ports since U.S. ended its sanctions waivers allowing a handful of countries to buy Iranian oil, Bloomberg reports.

Tanker tracking data cannot be fully accurate, as ships can turn off their transponders making them invisible to tracking systems, but so far, no tanker has been observed leaving port or on open seas moving toward one of Iran’s main customers; such as China and India.

This does not mean that Iran is not somehow using tankers to ship crude, as non-Iranian tankers can turn off their transponders, load and get to open seas, without being seen on tracking systems.

The United States has made it clear that it wants to bring Iranian oil exports down to zero, and for that reason Washington announced on April 22 that it will not extend the exemptions it had offered eight countries for 6 months to buy a limited amount of Iranian oil.

U.S. sanctions on Iran’s oil exports is the most damaging to Iran’s struggling economy, wiping off billions of dollars in foreign currency earnings, which are vital for financing the import of essential food stuff and goods.