"It's beyond comprehension that this happened," one former passenger said

Former passengers of the California commercial diving boat that went down in flames early Monday, leading to the presumed death of 34 onboard, have said that they were shocked to learn of the tragedy as they always felt safe on the vessel.

It’s beyond comprehension that this happened,” Rhonda Ahrens told NBC News, explaining that she traveled on the boat with her family last summer. “The crew was always very proactive when we were on it.”

Other former passengers, who had all been on the vessel multiple times, echoed similar sentiments to the outlet.

“My trips on the Conception were always very smooth and uneventful,” Izaak Velaz said. “At no time during those trips did I feel unsafe, nor did I see any items that I would have considered red flags.”

“They’ve never had problems on that boat when I was on it,” Penny Gomez, 49, told NBC News. “Its a little cramped but that’s how dive boats are, it’s not a luxury dive boat.”

“I felt completely comfortable, absolutely 100 percent on that boat,” said Colleen Casey, 63.

Their comments are in contrast to Michelle Patton, a 36-year-old project manager for a healthcare company in Sacramento, who told PEOPLE she went on a trip on the boat in March. Patton said the vessel “immediately smelled fuel in the bunk and said it over and over again” to other divers, but brushed it off because she didn’t want to overreact. She further claimed that she did not recall ever being shown how to use the escape door.

A total of 39 people — 33 passengers and six crew members — were onboard the 75-foot Conception boat when the flames erupted just after 3 a.m. All but five crew members were asleep below deck.

Those five crew members managed to seek refuge on a nearby boat called the Grape Escape, which they traveled to via dinghy. The others have all been presumed dead.

Boat Fire California
Credit: AP/Shutterstock

Truth Aquatics owned and operated the Conception. The boat, out of Santa Barbara, and has been doing diving excursions since the 1970s.

Actor Rob Lowe tweeted on Monday that he had also been on the boat “many times.”

“My heart breaks for those onboard the Conception,” the Parks and Recreation actor, 55, wrote. “An unspeakable horror on a boat I’ve been on many times. My prayers and thoughts are with the families.”

The United States Coast Guard on Tuesday announced that they have suspended the search for survivors.

In a press conference livestreamed online by KEYT News, Coast Guard Los Angeles Long Beach Sector Commander Captain Monica Rochester told reporters after a nearly 24-hour-long search, no additional signs of distress or debris in connection to the fire had been located.

They staged a total of seven missions, which included three helicopter crews and multiple service assets covering 160 miles, Rochester said.

A total of 20 bodies, 11 female and nine male, were recovered Monday and have been brought back to the coroner’s bureau. An additional four to six bodies were seen by search and rescue divers, though the positioning of the sunken boat made them unable to reach the victims by nightfall.

“It is never an easy decision to suspend search efforts,” she explained. “We know this is a very difficult time for families and friends of the victims. … Our hearts, our thoughts are with the family and friends of the victims.”

As news broke of the fire, speculation spread that the passengers were “locked” in the sleeping quarters after the dispatcher on the distressing mayday call appeared to repeatedly use that term. However, at Tuesday’s press conference, Santa Barbara County’s Sheriff-Coroner Bill Brown said that wasn’t the case.

The below deck section of the boat had a stairwell and an escape hatch, he explained, both of which were blocked by fire.

Authorities from the Coast Guard and the National Transportation Safety Board are still investigating the cause of the fire.

U.S. Coast Guard Captain Monica Rochester said that the Conception “has been in full compliance,” though if implications that it only had one exit and no access to fire-fighting equipment are indeed true, it likely should not have been deemed safe, naval architect Charles Cushing told PEOPLE.

Rochester said at the Tuesday press conference that all vessels are required to have smoke detectors, fixed and portable fire-fighting systems, and that there are no locked doors in accommodation spaces on board.

All required systems were accounted for during the boat’s last inspection in August, Rochester said, though she was unsure if the inspection was August 2018 or 2019.

Boat Fire California
Credit: Ringo H W Chiu/AP/Shutterstock

Victims’ names have not been released by authorities, though crew members told their rescuers that three people on board, including a 17-year-old girl traveling with her family, were celebrating birthdays, according to the Los Angeles Times.

Sheriff-Coroner Brown said that a majority of those on board were from Santa Cruz, San Jose, and the Bay Area in California.

Meanwhile, Brett Harmeling identified his sister, marine biologist Kristy Finstad, as one of the likely victims.

“Thank You ALL for your unconditional love and support during this incredibly tragic time… No final word on my sister Kristy; however, it is likely she has transitioned to be with the good Lord,” he wrote on Facebook.

Brown said the bodies recovered will be identified through DNA testing, and that investigators are working with family members to obtain samples.

The Coast Guard spokeswoman said the agency is “working deliberately with the vessel owner-operator who is with us at the time.”

Truth Aquatics could not be immediately reached by PEOPLE. Representatives from the company declined to comment to other news outlets.