Chemical tanker MV Chem Pluto was struck by a drone off India's west coast but the origin of the strike and the amount of explosive used for it could be known after further forensic and technical scrutiny, according to an analysis by the Indian Navy on Monday following an initial inspection of the vessel after it arrived at Mumbai harbour.

The Navy's explosive ordnance disposal team carried out a detailed inspection of the Liberian-flagged vessel on its arrival at Mumbai harbour, two days after the ship was hit by a drone off in the Arabian Sea when it was on its way to New Mangalore port.

A Pentagon spokesperson said on Sunday that MV Chem Pluto was hit by "a one-way attack drone fired from Iran".

In view of spate of attacks on commercial vessels in the Arabian Sea, the Navy deployed P-8I long-range patrol aircraft for surveillance, and warships INS Mormugao, INS Kochi and INS Kolkata in the region to maintain "deterrent presence", Navy officials said.

Saturday's drone attack on MV Chem Pluto came amid increasing concerns over various commercial vessels being targeted reportedly by Iran-backed Houthi militants in the Red Sea and Gulf of Aden amid the Israel-Hamas conflict.

The vessel with 21 Indian and one Vietnamese crew, anchored at outer anchorage off Mumbai at 3:30 pm. It was escorted on its way to Mumbai by Indian Coast Guard ship ICGS Vikram.

"On her arrival, the Indian Navy explosive ordnance disposal team inspected the vessel to make a preliminary assessment of the type and nature of attack. The analysis of the area of attack and debris found on the ship points towards a drone attack," a Navy spokesperson said.

"However, further forensic and technical analysis will be required to establish the vector of attack including type and amount of explosive used," he said.

The spokesperson said a joint investigation by various agencies commenced following completion of the analysis of the vessel by the explosive ordnance team.

"MV Chem Pluto has been cleared for further operation by her company-in-charge at Mumbai. The ship is scheduled to undergo mandatory checks by the various inspecting authorities before undertaking ship to ship transfer of cargo," he said.

"This is likely to be followed by docking and repairs of the damaged portion of MV Chem Pluto," he said.

The official said three guided missile destroyers have been deployed in the Arabian Sea in view of spate of attacks on commercial vessels in the region.

MV Chem Pluto, carrying crude oil to New Mangalore port from Al Jubail port in Saudi Arabia, was struck about 217 nautical miles from Porbandar on Saturday. No one was injured in the incident.

A Gabon-flagged commercial crude oil tanker with 25 Indian crew members also came under a drone attack in the Southern Red Sea on Saturday but no one was injured, according to Indian officials and the US military.

"Considering the recent spate of attacks in the Arabian Sea, the Indian Navy has deployed guided missile destroyers, INS Mormugao, INS Kochi and INS Kolkata in various areas to maintain a deterrent presence," the official said.

He said long-range maritime reconnaissance P8I aircraft are being regularly tasked to maintain domain awareness.

"Western Naval Command's Maritime Operations Centre is actively monitoring the situation in close coordination with Coast Guard and all concerned agencies," he said.