The United Kingdom Maritime Trade Operations (UKMTO) says it has received a report of an “incident” in the southern Red Sea, Al Jazeera reports.

“It has been reported to UKMTO that a tanker witnessed a splash from an unknown projectile in close proximity to the vessel,” it said in a statement, adding that the vessel and crew were reported to be safe.

“Environmental impact is unconfirmed at present. Vessels are advised to transit with caution and report any suspicious activity to UKMTO while authorities continue to investigate,” it said.