De­bris from the Ti­tan sub­mersible has been re­turned to land af­ter a fa­tal im­plo­sion dur­ing its voy­age to the wreck of the Ti­tan­ic cap­tured the world’s at­ten­tion last week.

The re­turn of the de­bris to port in St. John’s, New­found­land and Labrador, is a key piece of the in­ves­ti­ga­tion in­to why the sub­mersible im­plod­ed, killing all five peo­ple on board. Twist­ed chunks of the 22-foot sub­mersible were un­loaded at a Cana­di­an Coast Guard pier on Wednes­day.

The Cana­di­an ship Hori­zon Arc­tic car­ried a re­mote­ly op­er­at­ed ve­hi­cle, or ROV, to search the ocean floor near the Ti­tan­ic wreck for pieces of the sub­mersible. Pelag­ic Re­search Ser­vices, a com­pa­ny with of­fices in Mass­a­chu­setts and New York that owns the ROV, said on Wednes­day that it has com­plet­ed off­shore op­er­a­tions.

Pelag­ic Re­search Ser­vices’ team is “still on mis­sion” and can­not com­ment on the on­go­ing Ti­tan in­ves­ti­ga­tion, which in­volves sev­er­al gov­ern­ment agen­cies in the U.S. and Cana­da, said Jeff Ma­honey, a spokesper­son for the com­pa­ny.

“They have been work­ing around the clock now for ten days, through the phys­i­cal and men­tal chal­lenges of this op­er­a­tion, and are anx­ious to fin­ish the mis­sion and re­turn to their loved ones,” Ma­honey said.

De­bris from the Ti­tan was lo­cat­ed about 12,500 feet (3,810 me­ters) un­der­wa­ter and rough­ly 1,600 feet (488 me­ters) from the Ti­tan­ic on the ocean floor, the Coast Guard said last week. The Coast Guard is lead­ing the in­ves­ti­ga­tion in­to why the sub­mersible im­plod­ed dur­ing its June 18 de­scent. Of­fi­cials an­nounced on June 22 that the sub­mersible had im­plod­ed and all five peo­ple on board were dead.

The Coast Guard has con­vened a Ma­rine Board of In­ves­ti­ga­tion in­to the im­plo­sion. That is the high­est lev­el of in­ves­ti­ga­tion con­duct­ed by the Coast Guard.

One of the ex­perts the Coast Guard con­sult­ed with dur­ing the search said an­a­lyz­ing the phys­i­cal ma­te­r­i­al of re­cov­ered de­bris could re­veal im­por­tant clues about what hap­pened to the Ti­tan. And there could be elec­tron­ic da­ta, said Carl Harts­field of the Woods Hole Oceano­graph­ic In­sti­tu­tion.

“Cer­tain­ly all the in­stru­ments on any deep sea ve­hi­cle, they record da­ta. They pass up da­ta. So the ques­tion is, is there any da­ta avail­able? And I re­al­ly don’t know the an­swer to that ques­tion,” he said Mon­day.

Rep­re­sen­ta­tives for Hori­zon Arc­tic did not re­spond to re­quests for com­ment.

Coast Guard rep­re­sen­ta­tives de­clined to com­ment on the in­ves­ti­ga­tion or the re­turn of de­bris to shore on Wednes­day. No bod­ies have been re­cov­ered, though Coast Guard of­fi­cials said days ear­li­er that they were tak­ing pre­cau­tions in case they en­coun­tered hu­man re­mains dur­ing the in­ves­ti­ga­tion.

Ocean Gate CEO and pi­lot Stock­ton Rush was k illed in the im­plo­sion along with two mem­bers of a promi­nent Pak­istani fam­i­ly, Shahza­da Da­wood and his son Sule­man Da­wood; British ad­ven­tur­er Hamish Hard­ing; and Ti­tan­ic ex­pert Paul-Hen­ri Nar­ge­o­let.

Rep­re­sen­ta­tives for the Na­tion­al Trans­porta­tion Safe­ty Board and Trans­porta­tion Safe­ty Board of Cana­da, which are both in­volved in the in­ves­ti­ga­tion, al­so de­clined to com­ment. The Na­tion­al Trans­porta­tion Safe­ty Board has said the Coast Guard has de­clared the loss of the Ti­tan sub­mersible to be a “ma­jor ma­rine ca­su­al­ty” and the Coast Guard will lead the in­ves­ti­ga­tion.

“We are not able to pro­vide any ad­di­tion­al in­for­ma­tion at this time as the in­ves­ti­ga­tion is on­go­ing,” said Liam Mac­Don­ald, a spokesper­son for the Trans­porta­tion Safe­ty Board of Cana­da.

A spokesper­son for the In­ter­na­tion­al Mar­itime Or­ga­ni­za­tion, the U.N.’s mar­itime agency, has said any in­ves­tiga­tive re­ports from the dis­as­ter would be sub­mit­ted for re­view. Mem­ber states of the IMO can al­so pro­pose changes such as stronger reg­u­la­tions of sub­mersibles.

Cur­rent­ly, the IMO has vol­un­tary safe­ty guide­lines for tourist sub­mersibles which in­clude re­quire­ments they be in­spect­ed, have emer­gency re­sponse plans, and have a cer­ti­fied pi­lot on board among oth­er re­quire­ments. Any safe­ty pro­pos­als would not like­ly be con­sid­ered by the IMO un­til its next Mar­itime Safe­ty Com­mit­tee which be­gins in May 2024.

Ocean­Gate Ex­pe­di­tions, the com­pa­ny that owned and op­er­at­ed the Ti­tan, is based in the U.S. but the sub­mersible was reg­is­tered in the Ba­hamas. The Ocean­Gate com­pa­ny in Everett, Wash­ing­ton closed when the Ti­tan was found. Mean­while, the Ti­tan’s moth­er ship, the Po­lar Prince, was from Cana­da.

The op­er­a­tor charged pas­sen­gers $250,000 each to par­tic­i­pate in the voy­age. The im­plo­sion of the Ti­tan has raised ques­tions about the safe­ty of pri­vate un­der­sea ex­plo­ration op­er­a­tions. The Coast Guard al­so wants to use the in­ves­ti­ga­tion to im­prove safe­ty of sub­mersibles.

PORT­LAND, Maine (AP)