An explosion at a port on Egypt’s Mediterranean coast set fire to two ships, including a U.S. gas storage tanker, according to maritime tracking firms.

The incident occurred at the Suez Canal port of Adabiya, where one of the vessels, the Gaslog Shanghai, a liquefied natural gas carrier, caught fire. The other ship, the Sea-Lion, a U.S.-flagged tanker, also sustained damage.

Egyptian authorities have not yet commented on the cause of the explosion, but maritime tracking firms suggest it may have been an apparent drone strike. The incident has raised concerns about the security of maritime traffic in the strategically important region.