Two oil tankers were hit by unidentified projectiles near the Strait of Hormuz on Friday. The attacks were reported by the United Kingdom Maritime Trade Operations agency.

The first vessel was struck while leaving the strait. It suffered a small fire and a blackout on board. The crew put out the fire and the ship resumed its voyage.

Hours later, a second tanker was hit east of Oman. All crew members were safe. No oil spill or environmental damage was reported in either incident.

The agency did not identify the projectiles or say who was responsible. It said authorities were investigating both strikes.

The attacks bring the number of tankers hit this week to seven, according to shipping data. That makes it tied for the fourth most violent week for vessels since the war began seven months ago.

Before US and Israeli strikes on Iran in late February, about a fifth of the world’s oil and liquefied natural gas passed through the strait. Tehran has since blocked commercial ships, and Washington has counter-blockaded Iranian ports.