US Coast Guard authorities suspended a search for a Marshall Islands sea ambulance, its crew of four and a further three passengers on Monday.

The Pacific Islanders have been missing for eight days since disappearing in nearby seas from the Marshall Islands' capital, Majuro, on March 3.

The search commenced two days after they failed to reach the Mili Atoll, located nearly 120 kilometres southeast of the port in Majuro.

However, the Marshall Islands government and the rescue taskforce says it remains committed to locate the missing vessel.

The Marshall Islands Health Ministry confirmed debris from the missing vessel had been found washed up at Imiej, Jaluit Atoll, west of their destination of Mili Atoll.

"Sea patrol vessels and Lomor boats continue active search operations," the taskforce has since said in a statement on Tuesday.

"Local authorities and community networks remain engaged in monitoring coastal areas for further findings.

"Search efforts will intensify based on the latest developments."

The names of the eight missing persons have not been released publicly.

The 37-foot fibreglass vessel had departed Majuro at 12:30pm for tuberculosis screening tests, the Marshall Islands Ministry of Health and Human Services confirmed.

Chief Warrant Officer Sara Muir, a spokesperson on behalf of the US Coast Guard Forces, Micronesia – Sector Guam, also released a heartfelt statement.

"We stand with both the families and the Republic of the Marshall Islands' community in their grief," she said.

"Our Navy and Marshallese partners poured extraordinary skill and resolve into this search across a vast Pacific expanse.

"Suspending active efforts doesn't diminish our respect for these mariners' lives or hope that answers may still come."

The captain, the crew, in addition to a nurse practitioner, a health assistant and a community outreach worker, did not return to Majuro by their expected arrival time days later, according to both the Coast Guard and the health ministry.

The missing vessel's captain was an experienced mariner, and the route was also a routine transit, Muir said searchers were told.

The search included a US Navy P-8 Poseidon patrol aircraft from Kadena Air Base, Okinawa prefecture off the Japan mainland; a Coast Guard HC-130 Hercules from Air Station Barbers Point, Hawaii; and two vessels from the Marshall Islands – the RMIS Lomor 03, a sea patrol vessel, and the LiWeton Mour, another sea ambulance.

Search parties faced challenging conditions in the "vast Pacific", Muir said.

A "little bit higher sea state with larger swells" also hindered visibility, she added.

The US Navy, Coast Guard and Marshall Islands' crews conducted more than 16 searches, covering around 135,692 kilometres – an area more than half the size of the state of Victoria – over more than 81 hours.

While Micronesian sailors are quite comfortable in their calming seas, search efforts in the region often last for many days, unlike in areas with far more extreme weather conditions.

"We know there's a chance, and we're always thrilled when we can find them," Muir said.

The vessel was equipped with communication and navigation systems capable of sending a distress call, but no signal was received, according to New Zealand public radio RNZ Pacific.

"It's always difficult when we don't find the people we're looking for," Muir said.

"Suspending an active search effort is never easy.

"It doesn't diminish respect for mariners' lives and hope that answers may come for their families."

The trip to sail from one atoll to another is not out of the ordinary for most seafaring residents of the Marshall Islands, which are the first country of the Pacific to initiate mass tuberculosis screenings.

The Marshall Islands has an extremely high incidence of tuberculosis – an infectious disease caused by bacteria that mostly affects the lungs but also other parts of the body – more than 50 times higher than in Australia.

The US Centres for Disease Control and Prevention collaborated with the Marshall Islands Health Ministry to train health care providers to recognise and treat tuberculosis.

While the Marshall Islands remains a sovereign nation, the territory's five main islands, 1220 tiny islands and 29 other coral atolls located just west of the International Date Line and just north of the equator, relies on the US for defence and security, under their 1983 Compact of Free Association of the US.