HMCS St. John's and its 220 crew members are being forced to leave a humanitarian mission in Turks and Caicos as another hurricane approaches the already devastated Caribbean islands.

Hurricane Maria, following on the path of Hurricanes Irma and Jose, is strengthening as it heads toward the Caribbean and Atlantic coast.

"We're keeping a close eye on the movement of now-Hurricane Maria, which will arrive here in the next 72 to 96 hours or so. Unfortunately, when that gets into the area, we'll have to depart the island to stay out of its path and avoid getting ourselves damaged by this storm," said Lt. Francois Belanger, who spoke to CBC News Monday from aboard the ship.

"So it's likely we'll be proceeding toward the southwest, outside of its path. But where we're going to go is not known at this time."

The crew of HMCS St. John’s works on cleanup operations at a school on South Caicos Island following Irma. (Master Cpl. Chris Ringius/Formation Imaging Services Halifax)

Crew members have been providing manpower to clear up debris and help repair damage to buildings on the islands. On Monday, a team of Canadian military personnel was repairing a school on South Caicos island.

Plumbing and electrical skills are in high demand, Belanger said.

However, the biggest challenge has been making the island's salt water desalination plant operational again following the damage it sustained during Irma, he said.

A CH-124 Sea King helicopter from HMCS St. John’s airlifts supplies to South Caicos island to provide humanitarian assistance in the wake of Irma's devastation. (Provided/Master Cpl. Chris Ringius/Formation Imaging Services Halifax)

"The wide knowledge of technical expertise that we provide as a warship was definitely welcome, especially at the salt water desalination plant," Belanger said.

The plant on South Caicos is expected to be back up and running within 24 to 36 hours, he said, adding HMCS St. John's can also produce drinkable water.

Every night, the ship goes out about 12 kilometres and desalinates sea water, producing hundreds of litres of drinking water, Belanger said. Crew then fill water bladders and transport the drinking water ashore daily by helicopter.

Leading Seaman Doiron from HMCS St. John's helps a local worker on South Caicos island. (Master Cpl. Chris Ringius/Formation Imaging Services Halifax)

Belanger said the frigate may return to the British archipelago after Maria has passed through.

That depends on a number of factors, including whether HMCS St. John's is required to help out in another, more severely damaged area, he said.