According to the National Iranian Tanker Company (NITC), the blasts damaged SABITI, which is owned by NITC, on its main storage tank.

NITC has said in a statement that the blasts were probably caused by missile strikes on the Iranian vessel.
Fortunately, all of the ship's crew members are safe and secure, and the vessel is currently in a stable condition, with only a slight damage on the ship’s body which is being repaired by the crew.
According to NITC, technical experts in the company's emergency room are investigating the situation and the causes of the accident.
No Fire in SABITI
NITC Public and International Relations has said contrary to some news, there has been no shipwreck or fire on SABITI. The ship is in a stable condition.
NITC also announced that the images posted on some social networks and news sites showing a ship being on fire do not belong to SABITI. The ship has not been set on fire and is in a stable condition and the crew-members are fortunately also in safe condition.
NITC denies any news regarding missile strike by Saudi Arabia to the Iranian tanker. The company's initial announcement concerning the case shall be regarded as the sole source of information.

NITC is investigating the source of the strikes.