A water taxi began to take on water and quickly sank off the coast of the western city of Jakobstad, prompting a rescue operation to save the 27 people onboard on Thursday afternoon.
An estimated 15-cm hole in the m/s Mässkär's hull caused it to take on water very quickly. But thanks to nearby boaters who rushed to the scene to help, everyone aboard was rescued before the vessel was completely submerged.
Hours after Thursday's harrowing incident one of the boat's three co-owners, Anders Boström, said he suspected the hole was caused by a malfunction in the boat engine's exhaust system.
A few rescued passengers told Yle there was a lot of smoke pouring out of the back of the boat before it began to take on water.
On Friday, another of the boat's co-owners, Stefan Bredbacka, gave his theory of why the boat started to burn and then sank.
He said the engine's muffler caught fire and created a hole in the vessel's hull.
"It was a hole around 15 cm in diameter. The muffler has been replaced at least a couple times before because it caught fire but the [fires] have not been as severe as this one," Bredbacka said.
Captain takes the fall
The boat's captain, Daniel Sjö, took responsibility for not thoroughly checking the boat, saying that Thursday's close-call was a result of human error.
"In hindsight, I should have checked the cooling system's valve before I started. If I had done that, nothing would have happened. It was a question of human error," he said.
The valve in question should have been left open rather than closed, as it was on Thursday, he said.
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Svenska Yle's bureau in Ostrobothnia spoke with a few of the rescued passengers on Thursday, who claimed the captain did not inform passengers what was happening as the incident unfolded.
Sjö, who's worked on sea boats for the past 60 years, said the situation was progressing so quickly that there was just not enough time..
"You don't have many minutes in this kind of circumstance, and the most important matters need to be addressed [first] he said. "Even as captain, you don't know with certainty what was happening before everything already happened."
Sjö said his wife, serving as first mate on the vessel, handed out life vests to all of the passengers.
"Then we put out all four of the emergency rafts," Sjö said.
The police, the Transport Safety Agency as well as the coast guard have interviewed Sjö about Thursday's events.
A preliminary criminal investigation has been launched by police and the coast guard. The agencies are trying to determine whether to bring charges relating to negligence in failing to ensure the ship was seaworthy, negligence regarding good seamanship as well as public endangerment.
Jari Nieminen from western Finland's coast guard said the probe would clarify whether Thursday's events correspond to the suspected violations.
At this point only the boat's captain, Sjö, is suspected of a crime, not the vessel's co-owners, Nieminen said.
He said that the investigation will take several weeks and that a technical inspection of the water bus has already begun.
Boat had too many passengers
The 10-meter long vessel, a Kulkuri 34, is registered to carry 22 passengers and two crew members, but was carrying a total of 27 people, which is three too many.
Sjö said that was his decision.
"I didn't want to leave three young girls on the shore, because they'd reserved their tickets far in advance," he said.
However, Sjö disputes allegations made by some that there were not enough life vests on the boat.
"Everyone had life vests and there were still enough [vests] for another group of people. There's always 50 percent more live vests onboard than necessary," Sjö said.
Sjö said he is relieved that no one was hurt on Thursday and that he will try to move on.
"I've been at sea for 60 years and plan to continue doing so," he said.
After the close call, the submerged Mässkär was retrieved and brought back to shore.
The boat's co-owner Bredbacka said he doubts the vessel will be shuttling passengers to Mässkär island again - at least by them.
"We really haven’t had the chance to think about it yet. It's possible to get the boat in good shape again, but I doubt that we will use it again," Bredbacka said, saying that he would prefer to use a larger boat with a deck on which passengers can sit and enjoy the summer sea.