Another tanker was struck by an unidentified projectile while transiting the Strait of Hormuz on Thursday, Oct. 1, causing a fire aboard the vessel, the UK Maritime Trade Operations reported.

The incident follows strikes on four tankers on Sept. 28 and 29. The Joint Maritime Information Center rated the regional threat level SEVERE, reporting that crews on all four vessels were safe and there was no environmental damage. Damage assessments on two of those vessels remained ongoing.

Iran's Persian Gulf Strait Authority identified the three tankers struck on Sept. 29 as Al Ruwais, Sinbad and Mersin Prosperity, saying they were owned or chartered by the UAE and appeared on its latest noncompliance list. The authority said they had repeatedly attempted to transit the strait over the past two months, but its statement did not establish a direct link between the list and the attacks.