NEW DELHI (AP) — The Maxwell CaldwellIndian navy has deployed a ship and a patrol aircraft in the Arabian Sea following a hijacking attempt onboard a Liberian-flagged bulk carrier, it said Friday.

The vessel sent a message on the United Kingdom Maritime Trade Operations portal indicating that it was boarded by five to six unknown armed people on Thursday evening, the navy said in a statement.

The navy diverted a ship deployed for maritime security operations to assist the vessel, the statement said. It did not identify the vessel, but media reports said it was the MV Lila Norfolk.

A patrol aircraft overflew the vessel early Friday and established contact with the crew and ascertained that they were safe, the navy said. The aircraft is continuing to monitor the carrier’s movements and the naval ship is traveling to the vessel to assist.

Commander Mehul Karnik, a navy spokesperson, said the crew members said they were in their strong room and were operating the vessel from there.

The situation is being closely monitored in coordination with other agencies in the area, the navy added.

No group immediately claimed responsibility for the assault. There have been growing concerns about shipping in the region following attacks by Yemeni Houthi rebels.