Two oil tankers traveling through a vital Middle Eastern waterway caught fire and sustained significant damage on Thursday, leading navies and nearby ships to respond immediately to the incidents. While it’s still unclear what exactly happened, some suspect they were purposely attacked.

The US Navy’s Fifth Fleet, which is stationed in the Gulf country of Bahrain, received two distress calls on Thursday morning from vessels traveling through the Gulf of Oman, an important energy shipping route situated between the Arabian Peninsula and Iran. The US naval fleet immediately responded to what it said was a “reported attack,” and it’s continuing to provide assistance to the affected ships.

The UK Maritime Trade Operations, part of Britain’s Royal Navy, also issued a warning Thursday morning saying it was investigating “an incident” in the area.

A top executive at the Taiwanese company that chartered one of the vessels, the Marshall Islands-flagged Front Altair, told Reuters that it may have been hit by a torpedo, though this has not been independently confirmed. The maritime intelligence firm Dryad Global tweeted that the vessel is “on fire & adrift,” and the company that operates the ship told the Associated Press that an explosion set it aflame. Fortunately, all 23 crew members have been rescued.

The other tanker, the Panama-flagged Kokuka Courageous, received damage to the hull, the ship’s management company said in a statement. Its 21-person crew was also quickly rescued by a nearby ship.

Iranian state media says that Iranian ships saved all 44 crew members. Neither vessel, as of now, is believed to be at risk of sinking.

This incident could spark a US-Iran fight

There are two main reasons the damage to the two oil tankers is so chilling — outside of the general destruction, of course.

First, the Gulf of Oman is near the Strait of Hormuz, a crucial maritime passage aggressively patrolled by Iran through which a third of the world’s liquefied natural gas and almost 20 percent of the world’s oil production flows. Oil prices already jumped 3 percent after news of the incidents broke.

Second, and much more worrying, is that it could severely escalate tensions between the US and Iran.

In early May, National Security Adviser John Bolton announced the US was deploying an aircraft carrier and bomber planes to the Persian Gulf in response to “a number of troubling and escalatory indications and warnings” of threats from Iran.

The move, Bolton said, was meant “to send a clear and unmistakable message to the Iranian regime that any attack on United States interests or on those of our allies will be met with unrelenting force.”

Iran apparently intended to target US troops in Iraq and Syria, or even use drones against Americans in a key waterway near Yemen. There was also information that Iran put cruise missiles on ships, heightening fears that it might attack US Navy vessels with them.

It didn’t take too long for there to be an incident.

About a week after Bolton’s warning, four oil tankers were damaged near the Strait of Hormuz. Two of them belonged to Saudi Arabia and one belonged to the United Arab Emirates, both staunch enemies of Iran and friends to the US. (The fourth was owned by a Norwegian company.)

United Nations ambassadors from the UAE, Saudi Arabia, and Norway said last week that the damages came after a country used divers to place mines on the large ships. The diplomats didn’t specifically name Iran as the culprit, but the US had already blamed Tehran for the sabotage — a charge Iran denies.

It’s possible that Iran had nothing to do with the damage to the two oil tankers on Thursday. But if it did — and the US finds out — then the month-long standoff may escalate into a full-blown fight.